Dual deblocking filter thresholds

ABSTRACT

Video coding using dual deblocking filter thresholds may include generating a reconstructed frame by decoding an encoded bitstream and outputting the reconstructed frame. Decoding may include generating a decoded block by decoding a portion of the encoded bitstream, identifying a first deblocking threshold index from the encoded bitstream, identifying a second deblocking threshold index from the encoded bitstream, generating a reconstructed block based on the decoded block, and including the reconstructed block in the reconstructed frame. Generating the reconstructed block may include deblocking based on the first deblocking threshold index and the second deblocking threshold index.

BACKGROUND

Digital video can be used, for example, for remote business meetings viavideo conferencing, high definition video entertainment, videoadvertisements, or sharing of user-generated videos. Due to the largeamount of data involved in video data, high-performance compression maybe advantageous for transmission and storage. Accordingly, it would beadvantageous to provide high-resolution video transmitted overcommunications channels having limited bandwidth, such as video codingusing dual deblocking filter thresholds.

SUMMARY

This application relates to encoding and decoding of video stream datafor transmission or storage. Disclosed herein are aspects of systems,methods, and apparatuses for encoding and decoding using dual deblockingfilter thresholds.

An aspect is a method for video decoding using dual deblocking filterthresholds. Video decoding using dual deblocking filter thresholds mayinclude generating a reconstructed frame by decoding an encodedbitstream and outputting the reconstructed frame. Decoding may includegenerating a decoded block by decoding a portion of the encodedbitstream, identifying a first deblocking threshold index from theencoded bitstream, identifying a second deblocking threshold index fromthe encoded bitstream, generating a reconstructed block based on thedecoded block, and including the reconstructed block in thereconstructed frame. Generating the reconstructed block may includedeblocking based on the first deblocking threshold index and the seconddeblocking threshold index.

Another aspect is a method for video encoding using dual deblockingfilter thresholds. Video encoding using dual deblocking filterthresholds may include generating an encoded frame by encoding an inputframe and outputting the output bitstream. Encoding may includegenerating a decoded frame by decoding the encoded frame, generating areconstructed frame by reconstructing the decoded frame, and generatingan output bitstream including the encoded frame, an indication of thefirst deblocking threshold index, and an indication of the seconddeblocking threshold index. Reconstructing the decoded frame may includeidentifying a joint deblocking threshold index from a plurality ofdeblocking threshold indexes for deblocking the decoded frame,identifying a first deblocking threshold index from the plurality ofdeblocking threshold indexes, wherein identifying the first deblockingthreshold index includes using the joint deblocking threshold index as asecond deblocking threshold index for deblocking the decoded frame, andidentifying the second deblocking threshold index from the plurality ofdeblocking threshold indexes, wherein identifying the second deblockingthreshold index includes using the first deblocking threshold index fordeblocking the decoded frame.

Another aspect is a method for video encoding using dual deblockingfilter thresholds. Video encoding using dual deblocking filterthresholds may include generating a reconstructed frame by generating adecoded frame including decoded blocks by decoding a portion of theencoded bitstream, identifying a first deblocking threshold index fromthe encoded bitstream, identifying a second deblocking threshold indexfrom the encoded bitstream, the second deblocking threshold indexdiffering from the first deblocking threshold index, generating apartially deblocked frame by deblocking the decoded frame in a firstdirection based on the first deblocking threshold index, and generatingthe reconstructed frame by deblocking the partially deblocked frame in asecond direction based on the second deblocking threshold index. Themethod may include and outputting the reconstructed frame.

Variations in these and other aspects will be described in additionaldetail hereafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIG. 1 is a diagram of a computing device in accordance withimplementations of this disclosure;

FIG. 2 is a diagram of a computing and communications system inaccordance with implementations of this disclosure;

FIG. 3 is a diagram of a video stream for use in encoding and decodingin accordance with implementations of this disclosure;

FIG. 4 is a block diagram of an encoder in accordance withimplementations of this disclosure;

FIG. 5 is a block diagram of a decoder in accordance withimplementations of this disclosure;

FIG. 6 is a block diagram of a representation of a portion of a frame inaccordance with implementations of this disclosure;

FIG. 7 shows an example of a portion of an input frame including blockboundaries in accordance with implementations of this disclosure.

FIG. 8 shows an example of a portion of a reconstructed frame includingblock artifacts in accordance with implementations of this disclosure.

FIG. 9 shows an example of a portion of a reconstructed frame includingblock artifacts with pixel granularity for a row of pixels in accordancewith implementations of this disclosure.

FIG. 10 shows an example of a portion of a reconstructed frame includingblock artifacts with pixel granularity for a column of pixels inaccordance with implementations of this disclosure.

FIG. 11 is a flowchart diagram of an example of encoding using dualdeblocking filter thresholds in accordance with implementations of thisdisclosure.

FIG. 12 is a flowchart diagram of an example of identifying deblockingthreshold indices in accordance with implementations of this disclosure.

FIG. 13 is a flowchart diagram of an example of identifying a deblockingthreshold index in accordance with implementations of this disclosure.

FIG. 14 is a flowchart diagram of an example of determining a currenterror metric in accordance with implementations of this disclosure.

FIG. 15 is a flowchart diagram of an example of deblocking a currentblock in accordance with implementations of this disclosure.

FIG. 16 is a flowchart diagram of an example of decoding using dualdeblocking filter thresholds in accordance with implementations of thisdisclosure.

DETAILED DESCRIPTION

Video compression schemes may include breaking each image, or frame,into smaller portions, such as blocks, and generating an outputbitstream using techniques to limit the information included for eachblock in the output. In some implementations, the information includedfor each block in the output may be limited by reducing spatialredundancy, reducing temporal redundancy, or a combination thereof. Forexample, temporal or spatial redundancies may be reduced by predicting aframe based on information available to both the encoder and decoder,and including information representing a difference, or residual,between the predicted frame and the original frame. The residualinformation may be further compressed by transforming the residualinformation into transform coefficients, quantizing the transformcoefficients, and entropy coding the quantized transform coefficients.

An encoded bitstream can be decoded to recreate the blocks and thesource images from the limited information. A decoded frame may includeartifacts, such as blocky artifacts that cross block boundaries causedby quantization. To reduce the artifacts, the decoded frame may befiltered, such as using a deblocking filter, along block boundaries,such as vertical block boundaries and horizontal block boundaries. Toretain edge content, such as an object edge, from the input image thataligns with the block boundaries, the filtering may identify thresholdvalues for determining whether to filter a respective block boundary andfor identifying corresponding filtering parameters. Filtering bothvertical block boundaries and horizontal block boundaries using one setof thresholds may limit the accuracy of the filtering and reduceencoding quality.

Video coding using dual deblocking filter thresholds may improveaccuracy and encoding quality by identifying a first optimal set offilter thresholds for filtering in a first direction, such as alongvertical block boundaries, and identifying a second optimal set offilter thresholds for filtering in a second direction, such as alonghorizontal block boundaries. An encoder may identify a deblockingthreshold index corresponding to the set of filter thresholds identifiedfor filtering vertical block boundaries and another deblocking thresholdindex corresponding to the set of filter thresholds identified forfiltering horizontal block. The encoder may include informationindicating the deblocking threshold indices in an encoded bitstream. Adecoder may extract the information indicating the deblocking thresholdindices from the encoded bitstream, identify the corresponding filterthresholds, and deblock a decoded frame using the first set of filterthresholds in the first direction and the second set of filterthresholds in the second direction.

FIG. 1 is a diagram of a computing device 100 in accordance withimplementations of this disclosure. The computing device 100 shownincludes a memory 110, a processor 120, a user interface (UI) 130, anelectronic communication unit 140, a sensor 150, a power source 160, anda bus 170. As used herein, the term “computing device” includes anyunit, or a combination of units, capable of performing any method, orany portion or portions thereof, disclosed herein.

The computing device 100 may be a stationary computing device, such as apersonal computer (PC), a server, a workstation, a minicomputer, or amainframe computer; or a mobile computing device, such as a mobiletelephone, a personal digital assistant (PDA), a laptop, or a tablet PC.Although shown as a single unit, any one element or elements of thecomputing device 100 can be integrated into any number of separatephysical units. For example, the user interface 130 and processor 120can be integrated in a first physical unit and the memory 110 can beintegrated in a second physical unit.

The memory 110 can include any non-transitory computer-usable orcomputer-readable medium, such as any tangible device that can, forexample, contain, store, communicate, or transport data 112,instructions 114, an operating system 116, or any information associatedtherewith, for use by or in connection with other components of thecomputing device 100. The non-transitory computer-usable orcomputer-readable medium can be, for example, a solid state drive, amemory card, removable media, a read-only memory (ROM), a random-accessmemory (RAM), any type of disk including a hard disk, a floppy disk, anoptical disk, a magnetic or optical card, an application-specificintegrated circuits (ASICs), or any type of non-transitory mediasuitable for storing electronic information, or any combination thereof.

Although shown a single unit, the memory 110 may include multiplephysical units, such as one or more primary memory units, such asrandom-access memory units, one or more secondary data storage units,such as disks, or a combination thereof. For example, the data 112, or aportion thereof, the instructions 114, or a portion thereof, or both,may be stored in a secondary storage unit and may be loaded or otherwisetransferred to a primary storage unit in conjunction with processing therespective data 112, executing the respective instructions 114, or both.In some implementations, the memory 110, or a portion thereof, may beremovable memory.

The data 112 can include information, such as input audio data, encodedaudio data, decoded audio data, or the like. The instructions 114 caninclude directions, such as code, for performing any method, or anyportion or portions thereof, disclosed herein. The instructions 114 canbe realized in hardware, software, or any combination thereof. Forexample, the instructions 114 may be implemented as information storedin the memory 110, such as a computer program, that may be executed bythe processor 120 to perform any of the respective methods, algorithms,aspects, or combinations thereof, as described herein.

Although shown as included in the memory 110, in some implementations,the instructions 114, or a portion thereof, may be implemented as aspecial purpose processor, or circuitry, that can include specializedhardware for carrying out any of the methods, algorithms, aspects, orcombinations thereof, as described herein. Portions of the instructions114 can be distributed across multiple processors on the same machine ordifferent machines or across a network such as a local area network, awide area network, the Internet, or a combination thereof.

The processor 120 can include any device or system capable ofmanipulating or processing a digital signal or other electronicinformation now-existing or hereafter developed, including opticalprocessors, quantum processors, molecular processors, or a combinationthereof. For example, the processor 120 can include a special purposeprocessor, a central processing unit (CPU), a digital signal processor(DSP), a plurality of microprocessors, one or more microprocessor inassociation with a DSP core, a controller, a microcontroller, anApplication Specific Integrated Circuit (ASIC), a Field ProgrammableGate Array (FPGA), a programmable logic array, programmable logiccontroller, microcode, firmware, any type of integrated circuit (IC), astate machine, or any combination thereof. As used herein, the term“processor” includes a single processor or multiple processors.

The user interface 130 can include any unit capable of interfacing witha user, such as a virtual or physical keypad, a touchpad, a display, atouch display, a speaker, a microphone, a video camera, a sensor, or anycombination thereof. For example, the user interface 130 may be anaudio-visual display device, and the computing device 100 may presentaudio, such as decoded audio, using the user interface 130 audio-visualdisplay device, such as in conjunction with displaying video, such asdecoded video. Although shown as a single unit, the user interface 130may include one or more physical units. For example, the user interface130 may include an audio interface for performing audio communicationwith a user, and a touch display for performing visual and touch-basedcommunication with the user.

The electronic communication unit 140 can transmit, receive, or transmitand receive signals via a wired or wireless electronic communicationmedium 180, such as a radio frequency (RF) communication medium, anultraviolet (UV) communication medium, a visible light communicationmedium, a fiber optic communication medium, a wireline communicationmedium, or a combination thereof. For example, as shown, the electroniccommunication unit 140 is operatively connected to an electroniccommunication interface 142, such as an antenna, configured tocommunicate via wireless signals.

Although the electronic communication interface 142 is shown as awireless antenna in FIG. 1, the electronic communication interface 142can be a wireless antenna, as shown, a wired communication port, such asan Ethernet port, an infrared port, a serial port, or any other wired orwireless unit capable of interfacing with a wired or wireless electroniccommunication medium 180. Although FIG. 1 shows a single electroniccommunication unit 140 and a single electronic communication interface142, any number of electronic communication units and any number ofelectronic communication interfaces can be used.

The sensor 150 may include, for example, an audio-sensing device, avisible light-sensing device, a motion sensing device, or a combinationthereof. For example, 100the sensor 150 may include a sound-sensingdevice, such as a microphone, or any other sound-sensing device nowexisting or hereafter developed that can sense sounds in the proximityof the computing device 100, such as speech or other utterances, made bya user operating the computing device 100. In another example, thesensor 150 may include a camera, or any other image-sensing device nowexisting or hereafter developed that can sense an image such as theimage of a user operating the computing device. Although a single sensor150 is shown, the computing device 100 may include a number of sensors150. For example, the computing device 100 may include a first cameraoriented with a field of view directed toward a user of the computingdevice 100 and a second camera oriented with a field of view directedaway from the user of the computing device 100.

The power source 160 can be any suitable device for powering thecomputing device 100. For example, the power source 160 can include awired external power source interface; one or more dry cell batteries,such as nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride(NiMH), lithium-ion (Li-ion); solar cells; fuel cells; or any otherdevice capable of powering the computing device 100. Although a singlepower source 160 is shown in FIG. 1, the computing device 100 mayinclude multiple power sources 160, such as a battery and a wiredexternal power source interface.

Although shown as separate units, the electronic communication unit 140,the electronic communication interface 142, the user interface 130, thepower source 160, or portions thereof, may be configured as a combinedunit. For example, the electronic communication unit 140, the electroniccommunication interface 142, the user interface 130, and the powersource 160 may be implemented as a communications port capable ofinterfacing with an external display device, providing communications,power, or both.

One or more of the memory 110, the processor 120, the user interface130, the electronic communication unit 140, the sensor 150, or the powersource 160, may be operatively coupled via a bus 170. Although a singlebus 170 is shown in FIG. 1, a computing device 100 may include multiplebuses. For example, the memory 110, the processor 120, the userinterface 130, the electronic communication unit 140, the sensor 150,and the bus 170 may receive power from the power source 160 via the bus170. In another example, the memory 110, the processor 120, the userinterface 130, the electronic communication unit 140, the sensor 150,the power source 160, or a combination thereof, may communicate data,such as by sending and receiving electronic signals, via the bus 170.

Although not shown separately in FIG. 1, one or more of the processor120, the user interface 130, the electronic communication unit 140, thesensor 150, or the power source 160 may include internal memory, such asan internal buffer or register. For example, the processor 120 mayinclude internal memory (not shown) and may read data 112 from thememory 110 into the internal memory (not shown) for processing.

Although shown as separate elements, the memory 110, the processor 120,the user interface 130, the electronic communication unit 140, thesensor 150, the power source 160, and the bus 170, or any combinationthereof can be integrated in one or more electronic units, circuits, orchips.

FIG. 2 is a diagram of a computing and communications system 200 inaccordance with implementations of this disclosure. The computing andcommunications system 200 shown includes computing and communicationdevices 100A, 100B, 100C, access points 210A, 210B, and a network 220.For example, the computing and communication system 200 can be amultiple access system that provides communication, such as voice,audio, data, video, messaging, broadcast, or a combination thereof, toone or more wired or wireless communicating devices, such as thecomputing and communication devices 100A, 100B, 100C. Although, forsimplicity, FIG. 2 shows three computing and communication devices 100A,100B, 100C, two access points 210A, 210B, and one network 220, anynumber of computing and communication devices, access points, andnetworks can be used.

A computing and communication device 100A, 100B, 100C can be, forexample, a computing device, such as the computing device 100 shown inFIG. 1. For example, the computing and communication devices 100A, 100Bmay be user devices, such as a mobile computing device, a laptop, a thinclient, or a smartphone, and the computing and communication device 100Cmay be a server, such as a mainframe or a cluster. Although thecomputing and communication device 100A and the computing andcommunication device 100B are described as user devices, and thecomputing and communication device 100C is described as a server, anycomputing and communication device may perform some or all of thefunctions of a server, some or all of the functions of a user device, orsome or all of the functions of a server and a user device. For example,the server computing and communication device 100C may receive, encode,process, store, transmit, or a combination thereof audio data and one orboth of the computing and communication device 100A and the computingand communication device 100B may receive, decode, process, store,present, or a combination thereof the audio data.

Each computing and communication device 100A, 100B, 100C, which mayinclude a user equipment (UE), a mobile station, a fixed or mobilesubscriber unit, a cellular telephone, a personal computer, a tabletcomputer, a server, consumer electronics, or any similar device, can beconfigured to perform wired or wireless communication, such as via thenetwork 220. For example, the computing and communication devices 100A,100B, 100C can be configured to transmit or receive wired or wirelesscommunication signals. Although each computing and communication device100A, 100B, 100C is shown as a single unit, a computing andcommunication device can include any number of interconnected elements.

Each access point 210A, 210B can be any type of device configured tocommunicate with a computing and communication device 100A, 100B, 100C,a network 220, or both via wired or wireless communication links 180A,180B, 180C. For example, an access point 210A, 210B can include a basestation, a base transceiver station (BTS), a Node-B, an enhanced Node-B(eNode-B), a Home Node-B (HNode-B), a wireless router, a wired router, ahub, a relay, a switch, or any similar wired or wireless device.Although each access point 210A, 210B is shown as a single unit, anaccess point can include any number of interconnected elements.

The network 220 can be any type of network configured to provideservices, such as voice, data, applications, voice over internetprotocol (VoIP), or any other communications protocol or combination ofcommunications protocols, over a wired or wireless communication link.For example, the network 220 can be a local area network (LAN), widearea network (WAN), virtual private network (VPN), a mobile or cellulartelephone network, the Internet, or any other means of electroniccommunication. The network can use a communication protocol, such as thetransmission control protocol (TCP), the user datagram protocol (UDP),the internet protocol (IP), the real-time transport protocol (RTP) theHyperText Transport Protocol (HTTP), or a combination thereof.

The computing and communication devices 100A, 100B, 100C can communicatewith each other via the network 220 using one or more a wired orwireless communication links, or via a combination of wired and wirelesscommunication links. For example, as shown the computing andcommunication devices 100A, 100B can communicate via wirelesscommunication links 180A, 180B, and computing and communication device100C can communicate via a wired communication link 180C. Any of thecomputing and communication devices 100A, 100B, 100C may communicateusing any wired or wireless communication link, or links. For example, afirst computing and communication device 100A can communicate via afirst access point 210A using a first type of communication link, asecond computing and communication device 100B can communicate via asecond access point 210B using a second type of communication link, anda third computing and communication device 100C can communicate via athird access point (not shown) using a third type of communication link.Similarly, the access points 210A, 210B can communicate with the network220 via one or more types of wired or wireless communication links 230A,230B. Although FIG. 2 shows the computing and communication devices100A, 100B, 100C in communication via the network 220, the computing andcommunication devices 100A, 100B, 100C can communicate with each othervia any number of communication links, such as a direct wired orwireless communication link.

In some implementations, communications between one or more of thecomputing and communication device 100A, 100B, 100C may omitcommunicating via the network 220 and may include transferring data viaanother medium (not shown), such as a data storage device. For example,the server computing and communication device 100C may store audio data,such as encoded audio data, in a data storage device, such as a portabledata storage unit, and one or both of the computing and communicationdevice 100A or the computing and communication device 100B may access,read, or retrieve the stored audio data from the data storage unit, suchas by physically disconnecting the data storage device from the servercomputing and communication device 100C and physically connecting thedata storage device to the computing and communication device 100A orthe computing and communication device 100B.

Other implementations of the computing and communications system 200 arepossible. For example, in an implementation, the network 220 can be anad-hoc network and can omit one or more of the access points 210A, 210B.The computing and communications system 200 may include devices, units,or elements not shown in FIG. 2. For example, the computing andcommunications system 200 may include many more communicating devices,networks, and access points.

FIG. 3 is a diagram of a video stream 300 for use in encoding anddecoding in accordance with implementations of this disclosure. A videostream 300, such as a video stream captured by a video camera or a videostream generated by a computing device, may include a video sequence310. The video sequence 310 may include a sequence of adjacent frames320. Although three adjacent frames 320 are shown, the video sequence310 can include any number of adjacent frames 320.

Each frame 330 from the adjacent frames 320 may represent a single imagefrom the video stream. Although not shown in FIG. 3, a frame 330 mayinclude one or more segments, tiles, or planes, which may be coded, orotherwise processed, independently, such as in parallel. A frame 330 mayinclude blocks 340. Although not shown in FIG. 3, a block can includepixels. For example, a block can include a 16×16 group of pixels, an 8×8group of pixels, an 8×16 group of pixels, or any other group of pixels.Unless otherwise indicated herein, the term ‘block’ can include asuperblock, a macroblock, a segment, a slice, or any other portion of aframe. A frame, a block, a pixel, or a combination thereof can includedisplay information, such as luminance information, chrominanceinformation, or any other information that can be used to store, modify,communicate, or display the video stream or a portion thereof.

FIG. 4 is a block diagram of an encoder 400 in accordance withimplementations of this disclosure. Encoder 400 can be implemented in adevice, such as the computing device 100 shown in FIG. 1 or thecomputing and communication devices 100A, 100B, 100C shown in FIG. 2,as, for example, a computer software program stored in a data storageunit, such as the memory 110 shown in FIG. 1. The computer softwareprogram can include machine instructions that may be executed by aprocessor, such as the processor 120 shown in FIG. 1, and may cause thedevice to encode video data as described herein. The encoder 400 can beimplemented as specialized hardware included, for example, in computingdevice 100.

The encoder 400 can encode an input video stream 402, such as the videostream 300 shown in FIG. 3, to generate an encoded (compressed)bitstream 404. In some implementations, the encoder 400 may include aforward path for generating the compressed bitstream 404. The forwardpath may include an intra/inter prediction unit 410, a transform unit420, a quantization unit 430, an entropy encoding unit 440, or anycombination thereof. In some implementations, the encoder 400 mayinclude a reconstruction path (indicated by the broken connection lines)to reconstruct a frame for encoding of further blocks. Thereconstruction path may include a dequantization unit 450, an inversetransform unit 460, a reconstruction unit 470, a filtering unit 480, orany combination thereof. Other structural variations of the encoder 400can be used to encode the video stream 402.

For encoding the video stream 402, each frame within the video stream402 can be processed in units of blocks. Thus, a current block may beidentified from the blocks in a frame, and the current block may beencoded.

At the intra/inter prediction unit 410, the current block can be encodedusing either intra-frame prediction, which may be within a single frame,or inter-frame prediction, which may be from frame to frame.Intra-prediction may include generating a prediction block from samplesin the current frame that have been previously encoded andreconstructed. Inter-prediction may include generating a predictionblock from samples in one or more previously constructed referenceframes. Generating a prediction block for a current block in a currentframe may include performing motion estimation to generate a motionvector indicating an appropriate reference portion of the referenceframe.

The intra/inter prediction unit 410 may subtract the prediction blockfrom the current block (raw block) to produce a residual block. Thetransform unit 420 may perform a block-based transform, which mayinclude transforming the residual block into transform coefficients in,for example, the frequency domain. Examples of block-based transformsinclude the Karhunen-Loéve Transform (KLT), the Discrete CosineTransform (DCT), the Singular Value Decomposition Transform (SVD), andthe Asymmetric Discrete Sine Transform (ADST). In an example, the DCTmay include transforming a block into the frequency domain. The DCT mayinclude using transform coefficient values based on spatial frequency,with the lowest frequency (i.e. DC) coefficient at the top-left of thematrix and the highest frequency coefficient at the bottom-right of thematrix.

The quantization unit 430 may convert the transform coefficients intodiscrete quantum values, which may be referred to as quantized transformcoefficients or quantization levels. The quantized transformcoefficients can be entropy encoded by the entropy encoding unit 440 toproduce entropy-encoded coefficients. Entropy encoding can include usinga probability distribution metric. The entropy-encoded coefficients andinformation used to decode the block, which may include the type ofprediction used, motion vectors, and quantizer values, can be output tothe compressed bitstream 404. The compressed bitstream 404 can beformatted using various techniques, such as run-length encoding (RLE)and zero-run coding.

The reconstruction path can be used to maintain reference framesynchronization between the encoder 400 and a corresponding decoder,such as the decoder 500 shown in FIG. 5. The reconstruction path may besimilar to the decoding process discussed below and may include decodingthe encoded frame, or a portion thereof, which may include decoding anencoded block, which may include dequantizing the quantized transformcoefficients at the dequantization unit 450 and inverse transforming thedequantized transform coefficients at the inverse transform unit 460 toproduce a derivative residual block. The reconstruction unit 470 may addthe prediction block generated by the intra/inter prediction unit 410 tothe derivative residual block to create a decoded block. The filteringunit 480 can be applied to the decoded block to generate a reconstructedblock, which may reduce distortion, such as blocking artifacts. Althoughone filtering unit 480 is shown in FIG. 4, filtering the decoded blockmay include loop filtering, deblocking filtering, or other types offiltering or combinations of types of filtering. The reconstructed blockmay be stored or otherwise made accessible as a reconstructed block,which may be a portion of a reference frame, for encoding anotherportion of the current frame, another frame, or both, as indicated bythe broken line at 482. Coding information, such as deblocking thresholdindex values, for the frame may be encoded, included in the compressedbitstream 404, or both, as indicated by the broken line at 484.

Other variations of the encoder 400 can be used to encode the compressedbitstream 404. For example, a non-transform based encoder 400 canquantize the residual block directly without the transform unit 420. Insome implementations, the quantization unit 430 and the dequantizationunit 450 may be combined into a single unit.

FIG. 5 is a block diagram of a decoder 500 in accordance withimplementations of this disclosure. The decoder 500 can be implementedin a device, such as the computing device 100 shown in FIG. 1 or thecomputing and communication devices 100A, 100B, 100C shown in FIG. 2,as, for example, a computer software program stored in a data storageunit, such as the memory 110 shown in FIG. 1. The computer softwareprogram can include machine instructions that may be executed by aprocessor, such as the processor 120 shown in FIG. 1, and may cause thedevice to decode video data as described herein. The decoder 500 can beimplemented as specialized hardware included, for example, in computingdevice 100.

The decoder 500 may receive a compressed bitstream 502, such as thecompressed bitstream 404 shown in FIG. 4, and may decode the compressedbitstream 502 to generate an output video stream 504. The decoder 500may include an entropy decoding unit 510, a dequantization unit 520, aninverse transform unit 530, an intra/inter prediction unit 540, areconstruction unit 550, a filtering unit 560, or any combinationthereof. Other structural variations of the decoder 500 can be used todecode the compressed bitstream 502.

The entropy decoding unit 510 may decode data elements within thecompressed bitstream 502 using, for example, Context Adaptive BinaryArithmetic Decoding, to produce a set of quantized transformcoefficients. The dequantization unit 520 can dequantize the quantizedtransform coefficients, and the inverse transform unit 530 can inversetransform the dequantized transform coefficients to produce a derivativeresidual block, which may correspond to the derivative residual blockgenerated by the inverse transform unit 460 shown in FIG. 4. Usingheader information decoded from the compressed bitstream 502, theintra/inter prediction unit 540 may generate a prediction blockcorresponding to the prediction block created in the encoder 400. At thereconstruction unit 550, the prediction block can be added to thederivative residual block to create a decoded block. The filtering unit560 can be applied to the decoded block to reduce artifacts, such asblocking artifacts, which may include loop filtering, deblockingfiltering, or other types of filtering or combinations of types offiltering, and which may include generating a reconstructed block, whichmay be output as the output video stream 504.

Other variations of the decoder 500 can be used to decode the compressedbitstream 502. For example, the decoder 500 can produce the output videostream 504 without the deblocking filtering unit 570.

FIG. 6 is a block diagram of a representation of a portion 600 of aframe, such as the frame 330 shown in FIG. 3, in accordance withimplementations of this disclosure. As shown, the portion 600 of theframe includes four 64×64 blocks 610, in two rows and two columns in amatrix or Cartesian plane. In some implementations, a 64×64 block may bea maximum coding unit, N=64. Each 64×64 block may include four 32×32blocks 620. Each 32×32 block may include four 16×16 blocks 630. Each16×16 block may include four 8×8 blocks 640. Each 8×8 block 640 mayinclude four 4×4 blocks 650. Each 4×4 block 650 may include 16 pixels,which may be represented in four rows and four columns in eachrespective block in the Cartesian plane or matrix. The pixels mayinclude information representing an image captured in the frame, such asluminance information, color information, and location information. Insome implementations, a block, such as a 16×16 pixel block as shown, mayinclude a luminance block 660, which may include luminance pixels 662;and two chrominance blocks 670, 680, such as a U or Cb chrominance block670, and a V or Cr chrominance block 680. The chrominance blocks 670,680 may include chrominance pixels 690. For example, the luminance block660 may include 16×16 luminance pixels 662 and each chrominance block670, 680 may include 8×8 chrominance pixels 690 as shown. Although onearrangement of blocks is shown, any arrangement may be used. AlthoughFIG. 6 shows N×N blocks, in some implementations, N×M blocks may beused. For example, 32×64 blocks, 64×32 blocks, 16×32 blocks, 32×16blocks, or any other size blocks may be used. In some implementations,N×2N blocks, 2N×N blocks, or a combination thereof may be used.

In some implementations, video coding may include ordered block-levelcoding. Ordered block-level coding may include coding blocks of a framein an order, such as raster-scan order, wherein blocks may be identifiedand processed starting with a block in the upper left corner of theframe, or portion of the frame, and proceeding along rows from left toright and from the top row to the bottom row, identifying each block inturn for processing. For example, the 64×64 block in the top row andleft column of a frame may be the first block coded and the 64×64 blockimmediately to the right of the first block may be the second blockcoded. The second row from the top may be the second row coded, suchthat the 64×64 block in the left column of the second row may be codedafter the 64×64 block in the rightmost column of the first row.

In some implementations, coding a block may include using quad-treecoding, which may include coding smaller block units within a block inraster-scan order. For example, the 64×64 block shown in the bottom leftcorner of the portion of the frame shown in FIG. 6, may be coded usingquad-tree coding wherein the top left 32×32 block may be coded, then thetop right 32×32 block may be coded, then the bottom left 32×32 block maybe coded, and then the bottom right 32×32 block may be coded. Each 32×32block may be coded using quad-tree coding wherein the top left 16×16block may be coded, then the top right 16×16 block may be coded, thenthe bottom left 16×16 block may be coded, and then the bottom right16×16 block may be coded. Each 16×16 block may be coded using quad-treecoding wherein the top left 8×8 block may be coded, then the top right8×8 block may be coded, then the bottom left 8×8 block may be coded, andthen the bottom right 8×8 block may be coded. Each 8×8 block may becoded using quad-tree coding wherein the top left 4×4 block may becoded, then the top right 4×4 block may be coded, then the bottom left4×4 block may be coded, and then the bottom right 4×4 block may becoded. In some implementations, 8×8 blocks may be omitted for a 16×16block, and the 16×16 block may be coded using quad-tree coding whereinthe top left 4×4 block may be coded, then the other 4×4 blocks in the16×16 block may be coded in raster-scan order.

In some implementations, video coding may include compressing theinformation included in an original, or input, frame by, for example,omitting some of the information in the original frame from acorresponding encoded frame. For example, coding may include reducingspectral redundancy, reducing spatial redundancy, reducing temporalredundancy, or a combination thereof.

In some implementations, reducing spectral redundancy may include usinga color model based on a luminance component (Y) and two chrominancecomponents (U and V or Cb and Cr), which may be referred to as the YUVor YCbCr color model, or color space. Using the YUV color model mayinclude using a relatively large amount of information to represent theluminance component of a portion of a frame, and using a relativelysmall amount of information to represent each corresponding chrominancecomponent for the portion of the frame. For example, a portion of aframe may be represented by a high-resolution luminance component, whichmay include a 16×16 block of pixels, and by two lower resolutionchrominance components, each of which represents the portion of theframe as an 8×8 block of pixels. A pixel may indicate a value, forexample, a value in the range from 0 to 255, and may be stored ortransmitted using, for example, eight bits. Although this disclosure isdescribed in reference to the YUV color model, any color model may beused.

In some implementations, reducing spatial redundancy may includetransforming a block into the frequency domain using, for example, adiscrete cosine transform (DCT). For example, a unit of an encoder, suchas the transform unit 420 shown in FIG. 4, may perform a DCT usingtransform coefficient values based on spatial frequency.

In some implementations, reducing temporal redundancy may include usingsimilarities between frames to encode a frame using a relatively smallamount of data based on one or more reference frames, which may bepreviously encoded, decoded, and reconstructed frames of the videostream. For example, a block or pixel of a current frame may be similarto a spatially corresponding block or pixel of a reference frame. Insome implementations, a block or pixel of a current frame may be similarto block or pixel of a reference frame at a different spatial location,and reducing temporal redundancy may include generating motioninformation indicating the spatial difference, or translation, betweenthe location of the block or pixel in the current frame andcorresponding location of the block or pixel in the reference frame.

In some implementations, reducing temporal redundancy may includeidentifying a portion of a reference frame that corresponds to a currentblock or pixel of a current frame. For example, a reference frame, or aportion of a reference frame, which may be stored in memory, may besearched to identify a portion for generating a predictor to use forencoding a current block or pixel of the current frame with maximalefficiency. For example, the search may identify a portion of thereference frame for which the difference in pixel values between thecurrent block and a prediction block generated based on the portion ofthe reference frame is minimized, and may be referred to as motionsearching. In some implementations, the portion of the reference framesearched may be limited. For example, the portion of the reference framesearched, which may be referred to as the search area, may include alimited number of rows of the reference frame. In an example,identifying the portion of the reference frame for generating apredictor may include calculating a cost function, such as a sum ofabsolute differences (SAD), between the pixels of portions of the searcharea and the pixels of the current block.

In some implementations, the spatial difference between the location ofthe portion of the reference frame for generating a predictor in thereference frame and the current block in the current frame may berepresented as a motion vector. The difference in pixel values betweenthe predictor block and the current block may be referred to asdifferential data, residual data, a prediction error, or as a residualblock. In some implementations, generating motion vectors may bereferred to as motion estimation, and a pixel of a current block may beindicated based on location using Cartesian coordinates as f_(x,y).Similarly, a pixel of the search area of the reference frame may beindicated based on location using Cartesian coordinates as r_(x,y). Amotion vector (MV) for the current block may be determined based on, forexample, a SAD between the pixels of the current frame and thecorresponding pixels of the reference frame.

Although described herein with reference to matrix or Cartesianrepresentation of a frame for clarity, a frame may be stored,transmitted, processed, or any combination thereof, in any datastructure such that pixel values may be efficiently represented for aframe or image. For example, a frame may be stored, transmitted,processed, or any combination thereof, in a two-dimensional datastructure such as a matrix as shown, or in a one-dimensional datastructure, such as a vector array. In an implementation, arepresentation of the frame, such as a two-dimensional representation asshown, may correspond to a physical location in a rendering of the frameas an image. For example, a location in the top left corner of a blockin the top left corner of the frame may correspond with a physicallocation in the top left corner of a rendering of the frame as an image.

In some implementations, block-based coding efficiency may be improvedby partitioning input blocks into one or more prediction partitions,which may be rectangular, including square, partitions for predictioncoding. In some implementations, video coding using predictionpartitioning may include selecting a prediction partitioning scheme fromamong multiple candidate prediction partitioning schemes. For example,in some implementations, candidate prediction partitioning schemes for a64×64 coding unit may include rectangular size prediction partitionsranging in sizes from 4×4 to 64×64, such as 4×4, 4×8, 8×4, 8×8, 8×16,16×8, 16×16, 16×32, 32×16, 32×32, 32×64, 64×32, or 64×64. In someimplementations, video coding using prediction partitioning may includea full prediction partition search, which may include selecting aprediction partitioning scheme by encoding the coding unit using eachavailable candidate prediction partitioning scheme and selecting thebest scheme, such as the scheme that produces the least rate-distortionerror.

In some implementations, encoding a video frame may include identifyinga prediction partitioning scheme for encoding a current block, such asblock 610. In some implementations, identifying a predictionpartitioning scheme may include determining whether to encode the blockas a single prediction partition of maximum coding unit size, which maybe 64×64 as shown, or to partition the block into multiple predictionpartitions, which may correspond with the sub-blocks, such as the 32×32blocks 620 the 16×16 blocks 630, or the 8×8 blocks 640, as shown, andmay include determining whether to partition into one or more smallerprediction partitions. For example, a 64×64 block may be partitionedinto four 32×32 prediction partitions. Three of the four 32×32prediction partitions may be encoded as 32×32 prediction partitions andthe fourth 32×32 prediction partition may be further partitioned intofour 16×16 prediction partitions. Three of the four 16×16 predictionpartitions may be encoded as 16×16 prediction partitions and the fourth16×16 prediction partition may be further partitioned into four 8×8prediction partitions, each of which may be encoded as an 8×8 predictionpartition. In some implementations, identifying the predictionpartitioning scheme may include using a prediction partitioning decisiontree.

In some implementations, video coding for a current block may includeidentifying an optimal prediction coding mode from multiple candidateprediction coding modes, which may provide flexibility in handling videosignals with various statistical properties, and may improve thecompression efficiency. For example, a video coder may evaluate eachcandidate prediction coding mode to identify the optimal predictioncoding mode, which may be, for example, the prediction coding mode thatminimizes an error metric, such as a rate-distortion cost, for thecurrent block. In some implementations, the complexity of searching thecandidate prediction coding modes may be reduced by limiting the set ofavailable candidate prediction coding modes based on similaritiesbetween the current block and a corresponding prediction block. In someimplementations, the complexity of searching each candidate predictioncoding mode may be reduced by performing a directed refinement modesearch. For example, metrics may be generated for a limited set ofcandidate block sizes, such as 16×16, 8×8, and 4×4, the error metricassociated with each block size may be in descending order, andadditional candidate block sizes, such as 4×8 and 8×4 block sizes, maybe evaluated.

In some implementations, block-based coding efficiency may be improvedby partitioning a current residual block into one or more transformpartitions, which may be rectangular, including square, partitions fortransform coding. In some implementations, video coding using transformpartitioning may include selecting a uniform transform partitioningscheme. For example, a current residual block, such as block 610, may bea 64×64 block and may be transformed without partitioning using a 64×64transform.

Although not expressly shown in FIG. 6, a residual block may betransform partitioned using a uniform transform partitioning scheme. Forexample, a 64×64 residual block may be transform partitioned using auniform transform partitioning scheme including four 32×32 transformblocks, using a uniform transform partitioning scheme including sixteen16×16 transform blocks, using a uniform transform partitioning schemeincluding sixty-four 8×8 transform blocks, or using a uniform transformpartitioning scheme including 256 4×4 transform blocks.

In some implementations, video coding using transform partitioning mayinclude identifying multiple transform block sizes for a residual blockusing multiform transform partition coding. In some implementations,multiform transform partition coding may include recursively determiningwhether to transform a current block using a current block sizetransform or by partitioning the current block and multiform transformpartition coding each partition. For example, the bottom left block 610shown in FIG. 6 may be a 64×64 residual block, and multiform transformpartition coding may include determining whether to code the current64×64 residual block using a 64×64 transform or to code the 64×64residual block by partitioning the 64×64 residual block into partitions,such as four 32×32 blocks 620, and multiform transform partition codingeach partition. In some implementations, determining whether totransform partition the current block may be based on comparing a costfor encoding the current block using a current block size transform to asum of costs for encoding each partition using partition sizetransforms.

FIG. 7 shows an example of a portion of an input frame including blockboundaries in accordance with implementations of this disclosure. Theportion 700 of the input frame includes a first block 710 at thetop-left, a second block 720 at the top-right, a third block 730 at thebottom-left, and a fourth block 740 at the bottom-right. The portion 700of the input frame includes a first block boundary 750, which is avertical block boundary, between the first block 710 and the secondblock 720, a second block boundary 760, which is a horizontal blockboundary, between the first block 710 and the third block 730, a thirdblock boundary 770, which is a vertical block boundary, between thethird block 730 and the fourth block 740, and a fourth block boundary780, which is a horizontal block boundary, between the second block 720and the fourth block 740.

The first block 710 and the second block 720 are shown with a stippledbackground to indicate that the first block 710 and the second block 720include content corresponding to a first object, or visual element,captured by the frame. The third block 730 and the fourth block 740 areshown with a white background to indicate that the third block 730 andthe fourth block 740 include content corresponding to a second object,or visual element, captured by the frame. The edge between the firstobject and the second object captured by the frame corresponds with thesecond block boundary 760 and the fourth block boundary 780 and isindicated by the thick broken line at 790.

Although not shown expressly in FIG. 7, each block 710, 720, 730, 740may include pixels. For example, each block 710, 720, 730, 740 may be an8×8 pixel block.

Encoding an image or video, such as the encoding described in relationto FIG. 4, may introduce artifacts or distortion, such as blockyartifacts, which may be distortion along block boundaries caused byquantization. For example, encoding the portion 700 of the input frameshown in FIG. 7 may introduce blocky artifacts as shown in thereconstructed image portion shown in FIG. 8.

FIG. 8 shows an example of a portion of a reconstructed frame includingblock artifacts in accordance with implementations of this disclosure.The portion 800 of the reconstructed frame shown in FIG. 8 maycorrespond to the portion 700 of the input frame shown in FIG. 7, exceptthat the portion 800 of the reconstructed frame shown in FIG. 8 includesblocky artifacts.

FIG. 8 includes a first block 810 at the top-left, a second block 820 atthe top-right, a third block 830 at the bottom-left, a fourth block 840at the bottom-right, a first block boundary 850, which is a verticalblock boundary, between the first block 810 and the second block 820, asecond block boundary 860, which is a horizontal block boundary, betweenthe first block 810 and the third block 830, a third block boundary 870,which is a vertical block boundary, between the third block 830 and thefourth block 840, and a fourth block boundary 880, which is a horizontalblock boundary, between the second block 820 and the fourth block 840.

The first block 810 shown in FIG. 8 corresponds to the first block 710shown in FIG. 7, except that the first block 810 shown in FIG. 8 isshown using dark stippling to indicate blocky quantization error. Thesecond block 820 shown in FIG. 8 corresponds to the second block 720shown in FIG. 7. The third block 830 shown in FIG. 8 corresponds to thethird block 730 shown in FIG. 7. The fourth block 840 shown in FIG. 8corresponds to the fourth block 740 shown in FIG. 7, except that thefourth block 840 shown in FIG. 8 is shown using light stippling toindicate blocky quantization error.

Similar to the objects described in relation to FIG. 7, the first block810 and the second block 820 shown in FIG. 8 include contentcorresponding to a first object, or visual element, captured by theframe, and the third block 830 and the fourth block 840 shown in FIG. 8include content corresponding to a second object, or visual element,captured by the frame. The edge between the first object and the secondobject captured by the frame corresponds with the second block boundary860 and the fourth block boundary 880 and is indicated by the thickbroken line at 890.

Although not shown expressly in FIG. 8, each block 810, 820, 830, 840may include pixels. For example, each block 810, 820, 830, 840 may be an8×8 pixel block.

Deblocking the portion 800 of the reconstructed frame shown in FIG. 8may include smoothing, or otherwise minimizing, blocky artifacts alongblock boundaries, such as the blocky artifacts along the first blockboundary 850 and the blocky artifacts along the third block boundary870, and preserving, or minimally blurring, the object edge 890 alongthe second block boundary 860 and the fourth block boundary 880, whichmay include distinguishing differences between block corresponding toblocky artifacts from differences between blocks corresponding to objectedges.

FIG. 9 shows an example of a portion of a reconstructed frame includingblock artifacts with pixel granularity for a row of pixels in accordancewith implementations of this disclosure. The portion 900 of thereconstructed frame shown in FIG. 9 may correspond to the portion 800 ofthe reconstructed frame shown in FIG. 8, except that in the portion 900of the reconstructed frame shown in FIG. 9 pixels, or pixel locations,for a row of pixels are expressly represented, and references to theblock boundaries are omitted for clarity.

FIG. 9 includes a first block 910 at the top-left, which corresponds tothe first block 810 shown in FIG. 8, a second block 920 at thetop-right, which corresponds to the second block 820 shown in FIG. 8, athird block 930 at the bottom-left, which corresponds to the third block830 shown in FIG. 8, and a fourth block 940 at the bottom-right, whichcorresponds to the fourth block 840 shown in FIG. 8.

The third block 930, which may be a current block, may include pixels,such as pixels along a row horizontally across the third block 930,which are labeled in FIG. 9, from left to right, c0, c1, c2, c3, c4, c5,c6, and c7 for clarity. The fourth block 940, which may be an adjacentblock, such as a horizontally adjacent block, may include pixels, suchas pixels along the row horizontally across the fourth block 940, whichare labeled in FIG. 9, from left to right, a0, a1, a2, a3, a4, a5, a6,and a7 for clarity.

Deblocking the third block 930 may include deblocking one or more of thepixels c0, c1, c2, c3, c4, c5, c6, c7 of a row of the current block(third block 930) along a block boundary between the current block(third block 930) and the horizontally adjacent block (fourth block940), which may correspond with the fourth block boundary 880 shown inFIG. 8,based on one or more of the pixels c0, c1, c2, c3, c4, c5, c6, c7along the row from the current block (third block 930) and the pixelsa0, a1, a2, a3, a4, a5, a6, a7 along the row from the adjacent block(fourth block 940).

Deblocking the second block 1020 may include deblocking one or more ofthe pixels c0, c1, c2, c3, c4, c5, c6, c7 of a column of the currentblock (second block 1020) along a block boundary between the currentblock (second block 1020) and the vertically adjacent block (fourthblock 1040), which may correspond with the third block boundary 870shown in FIG. 8, based on one or more of the pixels c0, c1, c2, c3, c4,c5, c6, c7 along the column from the current block (second block 1020)and the pixels a0, a1, a2, a3, a4, a5, a6, a7 along the column from thevertically adjacent block (fourth block 1040).

FIG. 10 shows an example of a portion of a reconstructed frame includingblock artifacts with pixel granularity for a column of pixels inaccordance with implementations of this disclosure. The portion 1000 ofthe reconstructed frame shown in FIG. 10 may correspond to the portion800 of the reconstructed frame shown in FIG. 8, except that in theportion 1000 of the reconstructed frame shown in FIG. 10 pixels, orpixel locations, for a column of pixels are expressly represented, andreferences to the block boundaries are omitted for clarity.

FIG. 10 includes a first block 1010 at the top-left, which correspondsto the first block 810 shown in FIG. 8, a second block 1020 at thetop-right, which corresponds to the second block 820 shown in FIG. 8, athird block 1030 at the bottom-left, which corresponds to the thirdblock 830 shown in FIG. 8, and a fourth block 1040 at the bottom-right,which corresponds to the fourth block 840 shown in FIG. 8.

The second block 1020, which may be a current block, may include pixels,such as pixels along a column vertically across the second block 1020,which are labeled in FIG. 10, from top to bottom, c0, c1, c2, c3, c4,c5, c6, and c7 for clarity. The fourth block 1040, which may be anadjacent block, such as a vertically adjacent block, may include pixels,such as pixels along the column vertically across the fourth block 1040,which are labeled in FIG. 10, from top to bottom, a0, a1, a2, a3, a4,a5, a6, and a7 for clarity.

Deblocking the second block 1020 may include deblocking one or more ofthe pixels c0, c1, c2, c3, c4, c5, c6, c7 of a column of the currentblock (second block 1020) along a block boundary between the currentblock (second block 1020) and the vertically adjacent block (fourthblock 1040), which may correspond with the third block boundary 870shown in FIG. 8, based on one or more of the pixels c0, c1, c2, c3, c4,c5, c6, c7 along the column from the current block (second block 1020)and the pixels a0, a1, a2, a3, a4, a5, a6, a7 along the column from thevertically adjacent block (fourth block 1040).

FIG. 11 is a flowchart diagram of an example of encoding using dualdeblocking filter thresholds 1100 in accordance with implementations ofthis disclosure. Encoding using dual deblocking filter thresholds 1100may be implemented in an encoder, such as the encoder 400 shown in FIG.4. For example, the filtering unit 480 of the encoder 400 shown in FIG.4 may implement encoding using dual deblocking filter thresholds 1100.

Encoding using dual deblocking filter thresholds 1100 may includeidentifying an input frame at 1110, encoding the input frame at 1120,outputting an encoded bitstream at 1130, or any combination thereof.

An input frame may be identified at 1110. For example, the encoder mayreceive, or otherwise access, an input image or input video stream orsignal, or a portion thereof, and may identify the input image or aportion of the input video stream as the current input frame.

The input frame identified at 1110 may be encoded at 1120. Encoding theinput frame at 1120 may include generating an encoded frame at 1122,generating a reconstructed frame at 1124, identifying deblockingthreshold indices at 1126, including the encoded frame and thedeblocking threshold indices in an output bitstream at 1128, or acombination thereof. Although shown separately in FIG. 11, generatingthe encoded frame at 1122, generating the reconstructed frame at 1124,identifying deblocking threshold indices at 1126, and including theencoded frame and the deblocking threshold indices in an outputbitstream at 1128 may be implemented in combination.

Generating the encoded frame at 1122, which may include using blockbased encoding, may be similar to the encoding described in relation toFIG. 4, except as described herein or otherwise clear from context. Forexample, the encoder may generate prediction blocks, identify adifference between respective prediction blocks and corresponding inputblocks as residuals, identify respective transform coefficients bytransforming the residuals, generate respective quantized transformcoefficients by quantizing the transform coefficients, entropy code therespective quantized transform coefficients and other encoding data,such as motion information, or a combination thereof.

Generating the reconstructed frame at 1124 may be similar to thereconstruction described in relation to FIG. 4, except as describedherein or otherwise clear from context. For example, the encoder maydequantize the quantized transform coefficients to generate respectivedequantized transform coefficients, inverse transform the dequantizedtransform coefficients to generate respective reconstructed residuals,identify respective prediction blocks, such as the prediction blocksgenerated at 1122, generate a decoded frame, which may includegenerating respective decoded blocks of the decoded frame by combiningthe respective prediction blocks and the corresponding reconstructedresiduals, filtering, such as loop filtering, deblocking filtering, orboth, the decoded frame to reduce artifacts and to generate thereconstructed frame, or a combination thereof. Although described inrelation to generating the reconstructed frame at 1124, deblocking, or aportion thereof, may be performed subsequent to generating the decodedframe or subsequent to loop filtering. The reconstructed frame may bestored or otherwise made accessible as a reconstructed, or referenceframe, for encoding another frame.

Deblocking threshold indices may be identified at 1126. In someimplementations, identifying the deblocking threshold indices at 1126may be performed subsequent to generating the encoded frame at 1122,concurrent with, such as in combination with, generating thereconstructed frame at 1124, or subsequent to generating thereconstructed frame at 1124. For example, although generating thereconstructed frame at 1124 and identifying deblocking threshold indicesat 1126 are shown separately in FIG. 11, the deblocking described inrelation to generating the reconstructed frame at 1124 may includeidentifying the deblocking threshold indices.

Identifying the deblocking threshold indices at 1126 may includeidentifying a first deblocking threshold index, identifying a seconddeblocking threshold index, or both. A deblocking threshold index may bean index, such as an integer value, that identifies a defined set,group, or collection of deblocking thresholds. For example, the encodermay include, or otherwise access, a table, or other data storagestructure, that includes the defined sets of deblocking thresholds,wherein each defined set of deblocking thresholds is indexed, oruniquely identified, by a respective corresponding deblocking thresholdindex.

Identifying the deblocking threshold indices at 1126 may includeidentifying the first deblocking threshold index for deblocking theframe in a first direction, such as horizontal or vertical, andidentifying the second deblocking threshold index, which may differ fromthe first deblocking threshold index, for deblocking the frame in asecond direction, orthogonal to the first direction, such as vertical orhorizontal.

In an example, the first deblocking threshold index may be identifiedfor deblocking vertical block boundaries from the frame and the seconddeblocking threshold index may be identified for deblocking horizontalblock boundaries for the frame. An example of identifying deblockingthreshold indices is shown in FIG. 12.

The encoded frame, the deblocking threshold indices, or both may beincluded in an output, or encoded, bitstream, at 1128. For example, thedeblocking threshold indices may be included in a frame header for theencoded frame, and the frame header may be included in the outputbitstream, which may include entropy coding the frame header, or aportion thereof.

Including the deblocking threshold indices in the output bitstream mayinclude including an indication of the first deblocking threshold indexin the output bitstream and, separately, including an indication of thesecond deblocking threshold index in the output bitstream. In someimplementations, including the an indication of the second deblockingthreshold index in the output bitstream may include identifying adifferential deblocking threshold index value, such as a differencebetween the first deblocking threshold index and the second deblockingthreshold index, and including the differential deblocking thresholdindex value, or an indication thereof, in the output bitstream as thesecond deblocking threshold index.

The encoded bitstream may be output at 1130. For example, the encodedbitstream, or output bitstream, may be transmitted as a signal via anetwork, such as the network 220 shown in FIG. 2, such that a device,such as the computing device 100 shown in FIG. 1 or the computing andcommunication devices 100A, 100B, 100C shown in FIG. 2, which mayinclude a decoder, such as the decoder 500 shown in FIG. 5, may receivethe signal via the network, may decode the encoded video bitstream, andmay generate a reconstructed frame, or a portion of a reconstructedframe, corresponding to the current frame. In another example, theencoded bitstream may be stored in a memory, such as the memory 110shown in FIG. 1, of a device, such as the computing device 100 shown inFIG. 1 or the computing and communication devices 100A, 100B, 100C shownin FIG. 2, as a stored encoded video, such that the device, or any otherdevice capable of accessing the memory, may retrieve the stored encodedvideo, such that a decoder, such as the decoder 500 shown in FIG. 5, maydecode the encoded video and may generate a reconstructed frame, or aportion of a reconstructed frame, corresponding to the current frame.

Other implementations of encoding using dual deblocking filterthresholds are available. In implementations, additional elements ofencoding using dual deblocking filter thresholds can be added, certainelements can be combined, and/or certain elements can be removed.

FIG. 12 is a flowchart diagram of an example of identifying deblockingthreshold indices 1200 in accordance with implementations of thisdisclosure. Identifying deblocking threshold indices 1200 may beimplemented in an encoder, such as the encoder 400 shown in FIG. 4. Forexample, the filtering unit 480 of the encoder 400 shown in FIG. 4 mayimplement identifying deblocking threshold indices 1200.

Identifying deblocking threshold indices 1200 may include identifyingdeblocking threshold indices for deblocking a current frame, which maybe a decoded frame, and may be similar to the identifying deblockingthreshold indices 726 shown in FIG. 7, except as described herein orotherwise clear from context.

Identifying deblocking threshold indices 1200 may include identifying ajoint deblocking threshold index at 1210, identifying a first distinctdeblocking threshold index at 1220, identifying a second distinctdeblocking threshold index at 1230, or any combination thereof.

Although not shown separately in FIG. 12, identifying deblockingthreshold indices 1200 may include identifying candidate deblockingthreshold indices. Each deblocking threshold index from the candidatedeblocking threshold indices may correspond with, and may uniquelyidentify, a respective defined set of deblocking thresholds. Forexample, the encoder, or a deblocking threshold index identificationunit of the encoder, may read from, or otherwise access, a table, orother data storage structure, that includes the candidate deblockingthreshold indices and corresponding sets of deblocking thresholds, suchas a table stored in a memory of the encoder, or otherwise accessible bythe encoder. In an example, the candidate deblocking threshold indicesmay have a cardinality of N, the defined sets of deblocking thresholdsmay have a cardinality of N, and each candidate deblocking thresholdindex may correspond to a respective defined set of deblockingthresholds.

Identifying the joint deblocking threshold index at 1210 may includeidentifying the deblocking threshold index corresponding to the set ofdeblocking thresholds that minimizes a metric, such as a joint errormetric, for deblocking the frame, which may include deblocking the frameusing the set of deblocking thresholds in a first direction, such ashorizontal or vertical, and deblocking the frame using the set ofdeblocking thresholds in a second direction, which may be orthogonal tothe first direction, such as vertical or horizontal. An example ofidentifying a deblocking threshold index, such as a joint deblockingthreshold index, is shown in FIG. 13.

Identifying the first distinct deblocking threshold index at 1220 mayinclude identifying the deblocking threshold index corresponding to theset of deblocking thresholds that minimizes a metrics, such as an errormetric, for deblocking the frame using the set of deblocking thresholdscorresponding to the first distinct deblocking threshold index in thefirst direction and using the set of deblocking thresholds correspondingto the joint deblocking threshold index identified at 1210 in the seconddirection. An example of identifying a deblocking threshold index, suchas the first distinct deblocking threshold index, is shown in FIG. 13.

Identifying the second distinct deblocking threshold index at 1230 mayinclude identifying the deblocking threshold index corresponding to theset of deblocking thresholds that minimizes a metric, such as an errormetric, for deblocking the frame using the set of deblocking thresholdscorresponding to the first distinct deblocking threshold indexidentified at 1220 in the first direction and using the set ofdeblocking thresholds corresponding to the second distinct deblockingthreshold index in the second direction. An example of identifying adeblocking threshold index, such as the second distinct deblockingthreshold index, is shown in FIG. 13.

FIG. 13 is a flowchart diagram of an example of identifying a deblockingthreshold index 1300 in accordance with implementations of thisdisclosure. Identifying a deblocking threshold index 1300 may beimplemented in an encoder, such as the encoder 400 shown in FIG. 4. Forexample, the filtering unit 480 of the encoder 400 shown in FIG. 4 mayimplement identifying a deblocking threshold index 1300.

Identifying a deblocking threshold index 1300 may include identifying acurrent candidate deblocking threshold index at 1310, determining acurrent error metric at 1320, identifying the candidate deblockingthreshold index corresponding to a minimal error metric at 1330, or anycombination thereof.

A current candidate deblocking threshold index may be identified at1310. Identifying the current candidate deblocking threshold index mayinclude identifying the current deblocking threshold index from a set ofcandidate deblocking threshold indices, such as the candidate deblockingthreshold indices described in relation to FIG. 12. Identifying thecurrent candidate deblocking threshold index at 1310 may includeidentifying a corresponding set of deblocking thresholds.

For example, identifying a joint deblocking threshold index, such asshown at 1210 in FIG. 12, may include identifying the deblockingthreshold index 1300 and identifying the current candidate deblockingthreshold index at 1310 may include identifying a set of deblockingthresholds corresponding to the current candidate deblocking thresholdindex for deblocking the current frame, or the portion thereof, in the afirst direction, such as horizontal or vertical, and a second direction,which may be orthogonal to the first direction, such as vertical orhorizontal.

In another example, identifying a distinct deblocking threshold index,such as shown at 1220 in FIG. 12 or as shown at 1230 in FIG. 12, mayinclude identifying the deblocking threshold index 1300 and identifyingthe current candidate deblocking threshold index at 1310 may includeidentifying a set of deblocking thresholds corresponding to the currentcandidate deblocking threshold index for deblocking the current frame,or the portion thereof, in the first direction and using a set ofdeblocking thresholds corresponding to a different distinct deblockingthreshold index, such as a separately, or previously, identifieddistinct deblocking threshold index, in the second direction, or usingthe set of deblocking thresholds corresponding to the different distinctdeblocking threshold index in the first direction and identifying theset of deblocking thresholds corresponding to the current candidatedeblocking threshold index for deblocking the current frame, or theportion thereof, in the second direction.

A current error metric may be determined for the current candidatedeblocking threshold index at 1320. Determining the current error metricmay include deblocking a current frame, or a portion thereof, using theset of deblocking thresholds corresponding to the current candidatedeblocking threshold index in a first direction, such as horizontal orvertical, deblocking the current frame, or the portion thereof, usingthe set of deblocking thresholds corresponding to the current candidatedeblocking threshold index in a second direction, which may beorthogonal to the first direction, such as vertical or horizontal, ordeblocking the current frame, or the portion thereof, using the set ofdeblocking thresholds corresponding to the current candidate deblockingthreshold index in the first direction and the second direction.

For example, identifying a joint deblocking threshold index, such asshown at 1210 in FIG. 12, may include identifying the deblockingthreshold index 1300 and determining the current error metric at 1320may include deblocking the current frame, or the portion thereof, usingthe set of deblocking thresholds corresponding to the current candidatedeblocking threshold index in the first direction and the seconddirection. In implementations including identifying a joint deblockingthreshold index, the current error metric may be a joint error metric.

In another example, identifying a distinct deblocking threshold index,such as shown at 1220 in FIG. 12 or as shown at 1230 in FIG. 12, mayinclude identifying the deblocking threshold index 1300 and determiningthe current error metric at 1320 may include deblocking the currentframe, or the portion thereof, using the set of deblocking thresholdscorresponding to the current candidate deblocking threshold index in thefirst direction and deblocking the current frame, or the portionthereof, using a set of deblocking thresholds corresponding to adifferent distinct deblocking threshold index, such as a separatelyidentified distinct deblocking threshold index, in the second direction,or deblocking the current frame, or the portion thereof, using the setof deblocking thresholds corresponding to the current candidatedeblocking threshold index in the second direction and deblocking thecurrent frame, or the portion thereof, using the set of deblockingthresholds corresponding to the different distinct deblocking thresholdindex in the first direction.

Determining the current error metric at 1320 may include generating acandidate reconstructed frame, or a portion thereof, and identifying thecurrent error metric based on differences between the candidatereconstructed frame, or the portion thereof, and the corresponding inputframe, or the corresponding portion thereof, such as by determining asum of absolute differences (SAD), a sum of squared differences (SSD),or another error metric, between the candidate reconstructed frame andthe corresponding input frame. An example of determining a current errormetric is shown in FIG. 14.

Respective error metrics, each corresponding to deblocking the currentframe, or the portion thereof, in the first direction, deblocking thecurrent frame, or the portion thereof, in the second direction, ordeblocking the current frame, or the portion thereof, in the firstdirection and the second direction, using a corresponding candidatedeblocking threshold index from the candidate deblocking thresholdindices, may be determined, as indicated by the broken line arrow at1325.

For example, identifying a joint deblocking threshold index, such asshown at 1210 in FIG. 12, may include identifying the deblockingthreshold index 1300 and determining the current error metric at 1320may include determining respective error metrics, which may be jointerror metrics, using each respective candidate deblocking thresholdindex from the candidate deblocking threshold indices by deblocking thecurrent frame, or the portion thereof, using a respective set ofdeblocking thresholds corresponding to the respective candidatedeblocking threshold index in the first direction and the seconddirection.

In some implementations, identifying the current candidate deblockingthreshold index at 1310 may omit identifying a separately identifieddistinct deblocking threshold index from the candidate deblockingthreshold indices, such as a distinct deblocking threshold indexseparately identified for deblocking the current frame, or the portionthereof, in the first direction (or the second direction), as thecurrent candidate deblocking threshold index for deblocking the currentframe, or the portion thereof, in the second direction (or the firstdirection), and determining the respective error metrics may omitdetermining an error metric corresponding to deblocking the currentframe, or the portion thereof, using the separately identified distinctdeblocking threshold index in the first direction and the seconddirection.

For example, identifying a distinct deblocking threshold index, such asshown at 1220 in FIG. 12 or as shown at 1230 in FIG. 12, may includeidentifying the deblocking threshold index 1300 and determining thecurrent error metric at 1320 may include determining error metrics(first error metrics), respectively corresponding to each candidatedeblocking threshold index from the candidate deblocking thresholdindices that differs from, or other than, a distinct deblockingthreshold index, such as a separately identified distinct deblockingthreshold index, by deblocking the current frame, or the portionthereof, using the respective set of deblocking thresholds correspondingto the respective current candidate deblocking threshold index in thefirst direction and deblocking the current frame, or the portionthereof, using a set of deblocking thresholds corresponding to thedistinct deblocking threshold index in the second direction, or bydeblocking the current frame, or the portion thereof, using the set ofdeblocking thresholds corresponding to the different distinct deblockingthreshold index in the first direction and deblocking the current frame,or the portion thereof, using the respective set of deblockingthresholds corresponding to the current candidate deblocking thresholdindex in the second direction.

The deblocking threshold index corresponding to the minimal error metricmay be identified at 1330. Identifying the deblocking threshold indexcorresponding to the minimal error metric may include identifying theminimal error metric from a set of error metrics. Each error metric fromthe set of error metrics may correspond with a respective current errormetric determined at 1320.

For example, identifying the deblocking threshold index 1300 may includeidentifying a joint deblocking threshold index, such as shown at 1210 inFIG. 12, determining the current error metric at 1320 may includedetermining error metrics including a respective error metriccorresponding deblocking the current frame, or the portion thereof, inthe first direction and the second direction using the respective set ofdeblocking thresholds corresponding to each respective candidatedeblocking threshold index from the candidate deblocking thresholdindices, and identifying the deblocking threshold index at 1330 mayinclude identifying the minimal error metric from the error metricsdetermined at 1320, and identifying the candidate deblocking thresholdindex corresponding to the minimal error metric as the deblockingthreshold index at 1330.

In another example, identifying deblocking threshold indices, such asshown at 1200 in FIG. 12, may include identifying a joint deblockingthreshold index, such as shown at 1210 in FIG. 12, identifying a firstdistinct deblocking threshold index, such as shown at 1220 in FIG. 12,and identifying a second distinct deblocking threshold index, such asshown at 1230 in FIG. 12.

Identifying the joint deblocking threshold index may include identifyinga minimal joint error metric corresponding to deblocking the currentframe, or the portion thereof, in the first direction using a set ofdeblocking thresholds and deblocking the current frame, or the portionthereof, in the second direction using the set of deblocking thresholds.

Identifying the first distinct deblocking threshold index may includeidentifying the deblocking threshold index corresponding to the minimalerror metric from a set of error metrics including the minimal jointerror metric and including candidate error metrics corresponding todeblocking the current frame, or the portion thereof, in the firstdirection using the set of deblocking thresholds corresponding to thejoint deblocking threshold index and deblocking the current frame, orthe portion thereof, in the second direction using other sets ofdeblocking thresholds.

Identifying the second distinct deblocking threshold index may includeidentifying the deblocking threshold index corresponding to the minimalerror metric from a set of error metrics including the error metriccorresponding to the first distinct deblocking threshold index andincluding candidate error metrics corresponding to deblocking thecurrent frame, or the portion thereof, in the second direction using theset of deblocking thresholds corresponding to the first distinctdeblocking threshold index and deblocking the current frame, or theportion thereof, in the second direction using other sets of deblockingthresholds.

FIG. 14 is a flowchart diagram of an example of determining a currenterror metric 1400 in accordance with implementations of this disclosure.Determining a current error metric 1400 may be implemented in anencoder, such as the encoder 400 shown in FIG. 4. For example, thefiltering unit 480 of the encoder 400 shown in FIG. 4 may implementdetermining a current error metric 1400.

Determining a current error metric 1400 may include identifying acurrent block at 1410, generating a reconstructed block at 1420,determining an error metric at 1430, or any combination thereof.

Although not shown separately in FIG. 14, determining a current errormetric 1400 may include identifying a first set of deblocking thresholdsfor deblocking a current frame in a first direction, such as horizontalor vertical, and identifying a second set of deblocking thresholds fordeblocking the current frame in a second direction, which may beorthogonal to the first direction, such as vertical or horizontal.

The first set of deblocking thresholds may correspond to a jointdeblocking threshold index, such as the joint deblocking threshold indexidentified as shown at 1210 in FIG. 12, or may correspond to a firstdistinct deblocking threshold index, such as the first distinctdeblocking threshold index identified as shown at 1220 in FIG. 12. Thesecond set of deblocking thresholds may correspond to the joint distinctdeblocking threshold index or may correspond with a second distinctdeblocking threshold index, such as the second distinct deblockingthreshold index identified as shown at 1230 in FIG. 12.

A current block of the current frame may be identified at 1410. Forexample, the current frame may include blocks, such as predictionblocks, and a respective current block from the frame may be identifiedbased on a scan order, such as raster order. Although not shownseparately in FIG. 14, determining a current error metric 1400 mayinclude identifying information indicating transform block sizes for thecurrent block, one or more adjacent blocks, adjacent to the currentblock, or both.

A reconstructed block may be generated at 1420. The current frame may bea decoded frame, the current block identified at 1410 may be a decodedblock, and generating the reconstructed block at 1420 may includedeblocking the current block.

Deblocking the current block may include deblocking the current block,which may be a decoded block, using a first deblocking threshold indexfor deblocking the current block in the first direction and using asecond deblocking threshold index for deblocking the current block inthe second direction.

The first deblocking threshold index and the second deblocking thresholdindex may be a joint deblocking threshold index or the first deblockingthreshold index may differ from the second deblocking threshold index.For example, the identified deblocking threshold index may be a jointdeblocking threshold index and deblocking the current block may includeusing the identified deblocking threshold index as a horizontaldeblocking threshold index for deblocking the decoded block in ahorizontal direction and as a vertical deblocking threshold index fordeblocking the decoded block in a vertical direction, or using theidentified deblocking threshold index as a vertical deblocking thresholdindex for vertical deblocking the decoded block in a vertical directionand as a horizontal deblocking threshold index for horizontal deblockingthe decoded block in a horizontal direction. An example of deblocking acurrent block is shown in FIG. 15.

As shown in FIG. 14, determining the current error metric 1400 mayinclude generating a respective reconstructed block for each block ofthe current frame as indicated by the broken line arrow at 1425. Forexample, for each block of the current frame, a respective reconstructedblock may be generated at 1420, which may include deblocking the currentblock in the first direction and the second direction. Although notshown separately in FIG. 14, determining a current error metric 1400 mayinclude generating a respective partially reconstructed block for eachblock of the current frame by deblocking the respective current block inthe first direction and generating a reconstructed block for each blockof the current frame by deblocking the corresponding partiallyreconstructed block in the second direction.

A current error metric may be determined at 1430. The current errormetric may be determined based on differences between the currentreconstructed frame, or a portion thereof, and the corresponding inputframe, or a corresponding portion thereof, such as by determining a sumof absolute differences, a sum of squared differences, or another errormetric, between the current reconstructed frame and the correspondinginput frame.

FIG. 15 is a flowchart diagram of an example of deblocking a currentblock 1500 in accordance with implementations of this disclosure.Deblocking a current block 1500, which may include generating areconstructed block, may be implemented in an encoder, such as theencoder 400 shown in FIG. 4. For example, the filtering unit 480 of theencoder 400 shown in FIG. 4 may implement deblocking a current block1500.

Deblocking the current block may include deblocking the current blockbased on a first deblocking threshold index or based on the firstdeblocking threshold index and a second deblocking threshold index. Forexample, the first deblocking threshold index may be a joint deblockingthreshold index, and deblocking the current block may include deblockingthe current block in a first direction based on the joint deblockingthreshold index and deblocking the current block in a second directionbased on the joint deblocking threshold index. In another example, thefirst deblocking threshold index may be a first distinct deblockingthreshold index, the second deblocking threshold index may be a seconddistinct deblocking threshold index, and deblocking the current blockmay include deblocking the current block in a first direction based onthe first distinct deblocking threshold index and deblocking the currentblock in a second direction based on the second distinct deblockingthreshold index.

The current block may have block boundaries, borders, edges, or sides.For example, as shown in FIGS. 6-10, the current block may have fourblock boundaries, which may include two block boundaries in the verticaldirection, such as a top block boundary and a bottom block boundary, andtwo block boundaries in the horizontal direction such as a left blockboundary and a right block boundary. The current block may beimmediately adjacent to adjacent blocks, such as an adjacent block abovethe current block, which may be adjacent to the current block along thetop block boundary, an adjacent block below the current block, which maybe adjacent to the current block along the bottom block boundary, anadjacent block to the left of the current block, which may be adjacentto the current block along the left block boundary, and an adjacentblock to the right of the current block, which may be adjacent to thecurrent block along the right block boundary. Each of the current blockand the adjacent blocks may correspond to respective transform blocks.For example, the current block may be an N×N block and may correspondwith an N×N transform block, or the current block may correspond tosmaller transform blocks, such as x²N/x×N/x transform blocks.

As shown in FIG. 15, deblocking a current block 1500 may includeidentifying a current direction at 1510, identifying a current blockboundary at 1520, identifying a current subset of deblocking thresholdsat 1530, identifying pixels at 1540, determining a non-flatness factorat 1550, determining whether to deblock at 1560, identifying adeblocking parameter at 1570, or a combination thereof.

A current direction may be identified at 1510. For example, the currentdirection may be identified as a first direction, such as horizontal orvertical, or a second direction, which may be orthogonal to the firstdirection, such as vertical or horizontal.

Identifying the current direction at 1510 may include identifying acurrent deblocking threshold index for deblocking the current frame inthe current direction. For example, the current deblocking thresholdindex for deblocking the current frame in the current direction may beidentified as shown at 1310 in FIG. 13. Identifying the currentdeblocking threshold index for deblocking the current frame in thecurrent direction may include identifying a current set, group, orcollection of deblocking thresholds associated with the currentdeblocking threshold index for deblocking the current frame in thecurrent direction. For example, the encoder may read from, or otherwiseaccess, a table, or other data storage structure, that includes thecurrent deblocking threshold index and corresponding deblockingthresholds, such as a table stored in a memory of the encoder, orotherwise accessible by the encoder.

A current block boundary may be identified at 1520. For example, thecurrent direction may be vertical and the horizontal block boundarycorresponding to the top side, border, or edge of the current block maybe identified as the current block boundary or the horizontal blockboundary corresponding to the bottom side, border, or edge of thecurrent block may be identified as the current block boundary. Inanother example, the current direction may be horizontal and thevertical block boundary corresponding to the left side, border, or edgeof the current block may be identified as the current block boundary orthe vertical block boundary corresponding to the right side, border, oredge of the current block may be identified as the current blockboundary.

A current subset of deblocking thresholds may be identified fordeblocking the current block boundary at 1530. Identifying the currentsubset of deblocking thresholds at 1530 may include identifying acurrent minimum transform block size corresponding to the current blockboundary identified at 1520.

Identifying the current minimum transform block size corresponding tothe current block boundary at 1530 may include identifying the transformblock sizes for each transform block along the current block boundary,which may include transform blocks corresponding to the current block,transform blocks adjacent to the current block along the current blockboundary, or both.

For example, referring to FIG. 8, the current block may be the top-rightblock 820, the current direction may be horizontal, the current blockboundary 850 may be the vertical boundary between the current block 820and the horizontally adjacent block 810, the current block 820 may be a16×16 block, the transform block size for the current block 820 may be16×16, the transform block size for the adjacent block 810 may be 8×8,and the current minimum transform block size may be 8×8.

Referring to FIG. 15, identifying current subset of deblockingthresholds at 1530 may include identifying the current subset ofdeblocking thresholds based on the current minimum transform block size,which may include identifying the current subset of deblockingthresholds from the current set of deblocking thresholds, which may bethe set of deblocking thresholds identified based on the currentdeblocking threshold index.

For example, the current set of deblocking thresholds identified basedon the current deblocking threshold index may include a respectivesubset of deblocking thresholds corresponding to each respectiveavailable transform block size, and identifying current subset ofdeblocking thresholds at 1530 may include identifying the subset ofdeblocking thresholds corresponding to the current minimum transformblock size from the current set of deblocking thresholds. The currentsubset of deblocking thresholds may be identified as the currentdeblocking threshold. For example, one or more of the deblockingthresholds may be associated with a respective minimum transform blocksize, and a subset of the deblocking thresholds, associated with thecurrent minimum transform block size, may be identified as the currentdeblocking threshold.

In some implementations, the minimum transform block size for a firstblock boundary in the current direction may match a previouslyidentified minimum transform block size for the opposite block boundaryfrom the current block in the current direction and deblockingthresholds identified for deblocking the opposite block boundary may beidentified as the deblocking thresholds for deblocking the current blockboundary. In some implementations, the minimum transform block size forthe current block boundary in the current direction may differ from apreviously identified minimum transform block size for the oppositeblock boundary from the current block in the current direction and thedeblocking thresholds for deblocking the current block boundary may beidentified separately from the deblocking thresholds identified fordeblocking the opposite block boundary.

Identifying the current subset of deblocking thresholds at 1530 mayinclude identifying a current deblocking determination threshold fordeblocking the current block boundary. For example, the current subsetof deblocking thresholds identified at 1530 may include the currentdeblocking determination threshold and the current deblockingdetermination threshold may be identified from the current subset ofdeblocking thresholds.

Current pixels, such as a current set, group, or collection of pixels,may be identified at 1540. The current pixels may include pixels fromthe current block, an adjacent block adjacent to the current block alongthe current block boundary in the current direction, or both. Forexample, the current direction identified at 1510 may be vertical, thecurrent block may include columns of pixels, the adjacent block mayinclude corresponding columns of pixels, and identifying the currentpixels at 1540 may include identifying a defined cardinality, number, orcount, (N) of pixels from a current column of the current block, suchthe N pixels from the current column of the current block most proximateto the current block boundary, and may include identifying the definedcardinality of pixels from the current column of the adjacent block,such the N pixels from the current column of the adjacent block mostproximate to the current block boundary. In some implementations, thecardinality of pixels identified from the current block may differ fromthe cardinality of pixels identified from the adjacent block.

Metrics, such as non-flatness factors may be determined at 1550. Anon-flatness factor may indicate flatness, or non-flatness, for anidentified set of pixels. For example, a current non-flatness factor mayindicate flatness for an identified set of pixels from the currentblock, such as the pixels from the current block identified at 1540, andan adjacent non-flatness factor may indicate flatness, or non-flatness,for the corresponding pixels of the adjacent block. For example, theflatness, or non-flatness, metric or factor may indicate a maximumdifference among the respective pixels.

For example, with reference to FIG. 9, the current block may be thebottom left block 930, the current block boundary may be the verticalboundary between the current block 930 and the adjacent block 940, whichmay be an adjacent decoded block. A respective current flatness factormay be identified for each row of the current block 940, and arespective adjacent flatness factor may be identified for each row ofthe adjacent block 940. In an example, the current flatness factor forthe fifth row from the top of the current block 930 may be identifiedbased on the pixels labeled c0, c1, c2, c3, c4, c5, c6, c7 and theadjacent flatness factor for the fifth row from the top of the adjacentblock 940 may be identified based on the pixels labeled a0, a1, a2, a3,a4, a5, a6, a7.

In an example, the current flatness, or non-flatness, factor for thecurrent block (c) 930 may be identified based on the maximum of theabsolute value of a difference between the pixel labeled c4 and thepixel labeled c7, the absolute value of a difference between the pixellabeled c5 and the pixel labeled c7, and the absolute value of adifference between the pixel labeled c6 and the pixel labeled c7, whichmay be expressed as the following:

Nf(c)=max(|c4−c7|, |c5−c7|, |c6−c7|).    [Equation 1]

The corresponding adjacent flatness, or non-flatness, factor for theadjacent block (a) may be identified based on the maximum of theabsolute value of a difference between the pixel labeled a0 and thepixel labeled a1, the absolute value of a difference between the pixellabeled a0 and the pixel labeled a2, and the absolute value of adifference between the pixel labeled a0 and the pixel labeled a3, whichmay be expressed as the following:

Nf(a)=max(|a0−a1|, |a0−a2|, |a0−a3|).    [Equation 2]

In another example, with reference to FIG. 10, the current block may bethe top right block 1020, the current block boundary may be thehorizontal boundary between the current block 1020 and the verticallyadjacent block 1040. A current flatness factor may be identified foreach column of the current block 1020, and an adjacent flatness factormay be identified for each column of the adjacent block 1040. Forexample, the current flatness factor for the fifth column from the leftof the current block 1020 may be identified based on the pixels labeledc0, c1, c2, c3, c4, c5, c6, and c7 and the adjacent flatness factor forthe fifth column from the left of the adjacent block 1040 may beidentified based on the pixels labeled a0, a1, a2, a3, a4, a5, a6, anda7.

As shown in FIG. 15, a current deblocking determination may beidentified at 1560. For example, whether to deblock the pixelsidentified at 1540 may be determined at 1560 based on the currentdeblocking determination threshold identified at 1530 and thenon-flatness factors determined at 1550. For example, the current blockboundary may align with an edge in the content captured by the frame,and deblocking pixels along the current block boundary may be omitted.In another example, the block boundary may be unaligned with edges inthe content captured by the frame, and the pixels along the currentblock boundary may be deblocked.

Determining whether to deblock the pixels identified at 1540 from thecurrent block along the current block boundary may include determiningwhether the current non-flatness factor identified at 1550 for thecurrent row or column of the current block (Nf(c)) is less than thecurrent deblocking determination threshold value identified at 1530, anddetermining whether the adjacent non-flatness factor for the adjacentblock (Nf(a)) is less than the current deblocking determinationthreshold value.

For example, the current non-flatness factor for the current row orcolumn of the current block (Nf(a)) may be less than the deblockingdetermination threshold and the adjacent non-flatness factor for thecurrent row or column of the adjacent block (Nf(a)) may be less than thedeblocking determination threshold, and a determination indicatingdeblocking for the current row or column of the current block boundarymay be identified.

In another example, the current non-flatness factor for the current rowor column of the current block (Nf(a)) may be less than the deblockingdetermination threshold and the adjacent non-flatness factor for thecurrent row or column of the adjacent block (Nf(a)) may be at least,such as equal to or greater than, the deblocking determination thresholdand a determination indicating the omission of deblocking for thecurrent row or column of the current block boundary may be identified.

In another example, the current non-flatness factor for the current rowor column of the current block (Nf(a)) may be at least, such as equal toor greater than, the deblocking determination threshold and the adjacentnon-flatness factor for the current row or column of the adjacent block(Nf(a)) may be less than the deblocking determination threshold, and adetermination indicating the omission of deblocking for the current rowor column of the current block boundary may be identified.

In another example, the current non-flatness factor for the current rowor column of the current block (Nf(a)) may be at least, such as equal toor greater than, the deblocking determination threshold and the adjacentnon-flatness factor for the current row or column of the adjacent block(Nf(a)) may be at least, such as equal to or greater than, thedeblocking determination threshold, and a determination indicating theomission of deblocking for the current row or column of the currentblock boundary may be identified.

The deblocking determination identified at 1560 may indicate deblockingfor the pixels identified at 1540 and a deblocking parameter ordeblocking filter parameter, such as a deblocking filter, deblockingfilter type, deblocking filter strength, or a combination thereof, fordeblocking the pixels identified at 1540 may be identified at 1570.Identifying the deblocking parameter may include identifying one or moredeblocking filter thresholds, which may differ from the deblockingdetermination threshold, from the current subset of deblockingthresholds and identifying the deblocking parameter based on theidentified deblocking filter thresholds. For example, the deblockingfilter thresholds may be identified or adjusted based on predictionmode, motion vector consistency, transform block size, transform blocktype, or the like.

Deblocking a current block boundary may include identifying pixels at1540 for each row or column of the current block, determining anon-flatness factor at 1550 for each row or column of the current block,determining whether to deblock at 1560 for each row or column of thecurrent block, identifying a deblocking parameter at 1570 for each rowor column of the current block, or a combination thereof, as indicatedby the broken line arrows at 1562 and 1572.

Deblocking the current block in the current direction may includeidentifying each block boundary at 1520 for the current direction, andfor each respective block boundary, identifying the current subset ofdeblocking thresholds at 1530 for the respective block boundary,identifying pixels at 1540 for each row or column of the current blockfor the respective block boundary, determining a non-flatness factor at1550 for each row or column of the current block for the respectiveblock boundary, determining whether to deblock at 1560 for each row orcolumn of the current block for the respective block boundary,identifying a deblocking parameter at 1570 for each row or column of thecurrent block for the respective block boundary, or a combinationthereof, as indicated by the broken line arrow at 1574.

Deblocking the current block may include identifying each respectivedirection at 1510, and, for each respective direction, identifying eachblock boundary at 1520 for the respective direction, and for eachrespective block boundary, identifying the current subset of deblockingthresholds at 1530 for the respective block boundary, identifying pixelsat 1540 for each row or column of the current block for the respectiveblock boundary, determining a non-flatness factor at 1550 for each rowor column of the current block for the respective block boundary,determining whether to deblock at 1560 for each row or column of thecurrent block for the respective block boundary, identifying adeblocking parameter at 1570 for each row or column of the current blockfor the respective block boundary, or a combination thereof, asindicated by the broken line arrow at 1576.

FIG. 16 is a flowchart diagram of an example of decoding using dualdeblocking filter thresholds 1600 in accordance with implementations ofthis disclosure. Decoding using dual deblocking filter thresholds 1600may be implemented in a decoder, such as the decoder 500 shown in FIG.5.

Decoding using dual deblocking filter thresholds 1600 may includeidentifying an encoded frame at 1610, generating a decoded frame at1620, identifying deblocking threshold indices at 1630, generating areconstructed frame at 1640, outputting the reconstructed frame at 1650,or any combination thereof.

An encoded frame may be identified at 1610. For example, the decoder mayreceive, or otherwise access, an encoded bitstream and may identify theencoded frame from the encoded bitstream, or a portion thereof.

A decoded frame may be generated at 1620. For example, the decoded framemay be generated by decoding the encoded frame identified at 1610.Generating the decoded frame may include generating decoded blocks.Generating a decoded block may include decoding a portion of the encodedbitstream.

Deblocking threshold indices may be identified at 1630. For example, thedeblocking threshold indices may be identified by decoding, reading, orextracting the deblocking threshold indices from the encoded bitstream,such as from a frame header associated with or corresponding to thecurrent (reconstructed or decoded) frame.

Identifying the deblocking threshold indices may include identifying afirst deblocking threshold index from the encoded bitstream, identifyinga second deblocking threshold index from the encoded bitstream, or both.For example, identifying the deblocking threshold indices may includeidentifying the first deblocking threshold index for deblocking thecurrent frame in a first direction, such as horizontal or vertical, andidentifying the second deblocking threshold index for deblocking thecurrent frame in a second direction, such as vertical or horizontal.

In some implementations, identifying the second deblocking thresholdindex may include extracting information indicating the seconddeblocking threshold index, such as a differential deblocking thresholdindex value, from the encoded bitstream, and identifying a sum of thedifferential deblocking threshold index value and the first deblockingthreshold index as the second deblocking threshold index. In someimplementations, identifying the second deblocking threshold index mayinclude determining that the information indicating the seconddeblocking threshold index includes a differential deblocking thresholdindex value.

A reconstructed frame may be generated at 1640. Generating thereconstructed frame may include deblocking the decoded frame, which mayinclude generating reconstructed blocks, and deblocking thereconstructed blocks.

Deblocking the decoded frame may include deblocking each decoded blockfrom the frame, which may include identifying each respective decodedblock from the frame and generating a corresponding reconstructed blockby deblocking the respective decoded block, which may be similar to theblock identification indicated at 1410 in FIG. 14 and the blockreconstruction indicated at 1420 in FIG. 14, described as indicatedherein or otherwise clear from context. Deblocking the current block maybe similar to the deblocking shown in FIG. 15, except as describedherein or otherwise clear from context. For example, each reconstructedblock may be generated by deblocking a corresponding decoded block basedon the first deblocking threshold index and the second deblockingthreshold index. The reconstructed blocks may be included in thereconstructed frame.

For example, the first deblocking threshold index may be a verticaldeblocking threshold index, and generating the reconstructed frame mayinclude vertical deblocking based on the first deblocking thresholdindex and horizontal deblocking based on the second deblocking thresholdindex. In another example, the first deblocking threshold index may be ahorizontal deblocking threshold index and generating the reconstructedframe may include horizontal deblocking based on the first deblockingthreshold index and vertical deblocking based on the second deblockingthreshold index.

Deblocking in the first direction may include generating a partiallydeblocked frame by deblocking the decoded frame in the first directionbased on the first deblocking threshold index. Deblocking in the seconddirection may include generating the reconstructed frame by deblockingthe partially deblocked frame in the second direction based on thesecond deblocking threshold index.

Deblocking in the first direction, or the second direction, may includeidentifying a current deblocking threshold, which may include a set ofdeblocking thresholds, from sets of deblocking thresholds based on therespective (current) deblocking threshold index. For example, thedecoder, or a deblocking threshold identification unit of the decoder,may read from, or otherwise access, a table, or other data storagestructure, that includes sets of deblocking thresholds, such as a tablestored in a memory of the decoder, or otherwise accessible by thedecoder, and may identify a first set of deblocking thresholdscorresponding to the first deblocking threshold index and a second setof deblocking thresholds corresponding to the second deblockingthreshold index.

The reconstructed frame may be output at 1650. For example, thereconstructed frame may be included in an output video stream, such asthe output video stream 504 shown in FIG. 5, for storage or presentationto a user.

The words “example” or “exemplary” are used herein to mean serving as anexample, instance, or illustration. Any aspect or design describedherein as “example” or “exemplary” not necessarily to be construed aspreferred or advantageous over other aspects or designs. Rather, use ofthe words “example” or “exemplary” is intended to present concepts in aconcrete fashion. As used in this application, the term “or” is intendedto mean an inclusive “or” rather than an exclusive “or”. That is, unlessspecified otherwise, or clear from context, “X includes A or B” isintended to mean any of the natural inclusive permutations. That is, ifX includes A; X includes B; or X includes both A and B, then “X includesA or B” is satisfied under any of the foregoing instances. In addition,the articles “a” and “an” as used in this application and the appendedclaims should generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Moreover, use of the term “an embodiment” or “one embodiment” or“an implementation” or “one implementation” throughout is not intendedto mean the same embodiment or implementation unless described as such.As used herein, the terms “determine” and “identify”, or any variationsthereof, includes selecting, ascertaining, computing, looking up,receiving, determining, establishing, obtaining, or otherwiseidentifying or determining in any manner whatsoever using one or more ofthe devices shown in FIG. 1.

Further, for simplicity of explanation, although the figures anddescriptions herein may include sequences or series of steps or stages,elements of the methods disclosed herein can occur in various ordersand/or concurrently. Additionally, elements of the methods disclosedherein may occur with other elements not explicitly presented anddescribed herein. Furthermore, one or more elements of the methodsdescribed herein may be omitted from implementations of methods inaccordance with the disclosed subject matter.

The implementations of the transmitting computing and communicationdevice 100A and/or the receiving computing and communication device 100B(and the algorithms, methods, instructions, etc. stored thereon and/orexecuted thereby) can be realized in hardware, software, or anycombination thereof. The hardware can include, for example, computers,intellectual property (IP) cores, application-specific integratedcircuits (ASICs), programmable logic arrays, optical processors,programmable logic controllers, microcode, microcontrollers, servers,microprocessors, digital signal processors or any other suitablecircuit. In the claims, the term “processor” should be understood asencompassing any of the foregoing hardware, either singly or incombination. The terms “signal” and “data” are used interchangeably.Further, portions of the transmitting computing and communication device100A and the receiving computing and communication device 100B do notnecessarily have to be implemented in the same manner.

Further, in one implementation, for example, the transmitting computingand communication device 100A or the receiving computing andcommunication device 100B can be implemented using a computer programthat, when executed, carries out any of the respective methods,algorithms and/or instructions described herein. In addition oralternatively, for example, a special purpose computer/processor can beutilized which can contain specialized hardware for carrying out any ofthe methods, algorithms, or instructions described herein.

The transmitting computing and communication device 100A and receivingcomputing and communication device 100B can, for example, be implementedon computers in a real-time video system. Alternatively, thetransmitting computing and communication device 100A can be implementedon a server and the receiving computing and communication device 100Bcan be implemented on a device separate from the server, such as ahand-held communications device. In this instance, the transmittingcomputing and communication device 100A can encode content using anencoder 400 into an encoded video signal and transmit the encoded videosignal to the communications device. In turn, the communications devicecan then decode the encoded video signal using a decoder 500.Alternatively, the communications device can decode content storedlocally on the communications device, for example, content that was nottransmitted by the transmitting computing and communication device 100A.Other suitable transmitting computing and communication device 100A andreceiving computing and communication device 100B implementation schemesare available. For example, the receiving computing and communicationdevice 100B can be a generally stationary personal computer rather thana portable communications device and/or a device including an encoder400 may also include a decoder 500.

Further, all or a portion of implementations can take the form of acomputer program product accessible from, for example, a tangiblecomputer-usable or computer-readable medium. A computer-usable orcomputer-readable medium can be any device that can, for example,tangibly contain, store, communicate, or transport the program for useby or in connection with any processor. The medium can be, for example,an electronic, magnetic, optical, electromagnetic, or a semiconductordevice. Other suitable mediums are also available.

The above-described implementations have been described in order toallow easy understanding of the application are not limiting. On thecontrary, the application covers various modifications and equivalentarrangements included within the scope of the appended claims, whichscope is to be accorded the broadest interpretation so as to encompassall such modifications and equivalent structure as is permitted underthe law.

What is claimed is:
 1. A method comprising: generating, by a processorexecuting instructions stored on a non-transitory computer-readablemedium, a reconstructed frame by decoding an encoded bitstream, whereindecoding includes: generating a decoded block by decoding a portion ofthe encoded bitstream; identifying a first deblocking threshold indexfrom the encoded bitstream; identifying a second deblocking thresholdindex from the encoded bitstream; generating a reconstructed block basedon the decoded block, wherein generating the reconstructed blockincludes deblocking based on the first deblocking threshold index andthe second deblocking threshold index; including the reconstructed blockin the reconstructed frame; and outputting the reconstructed frame. 2.The method of claim 1, wherein identifying the first deblockingthreshold index includes extracting the first deblocking threshold indexfrom a frame header corresponding to the reconstructed frame.
 3. Themethod of claim 1, wherein identifying the second deblocking thresholdindex includes: identifying a differential deblocking threshold indexvalue from the encoded bitstream; and identifying a sum of thedifferential deblocking threshold index value and the first deblockingthreshold index as the second deblocking threshold index.
 4. The methodof claim 1, wherein generating the reconstructed frame includes: on acondition that the first deblocking threshold index is a verticaldeblocking threshold index, deblocking includes vertical deblockingbased on the first deblocking threshold index and horizontal deblockingbased on the second deblocking threshold index; and on a condition thatthe first deblocking threshold index is a horizontal deblockingthreshold index, deblocking includes horizontal deblocking based on thefirst deblocking threshold index and vertical deblocking based on thesecond deblocking threshold index.
 5. The method of claim 1, whereindeblocking includes: identifying a current deblocking threshold from aplurality of deblocking thresholds based on a current deblockingthreshold index, wherein: on a condition that the current deblockingthreshold index is the first deblocking threshold index, the currentdeblocking threshold is a first deblocking threshold; and on a conditionthat the current deblocking threshold index is the second deblockingthreshold index, the current deblocking threshold is a second deblockingthreshold.
 6. The method of claim 5, wherein identifying the currentdeblocking threshold includes: identifying a set of deblockingthresholds from the plurality of deblocking thresholds based on thecurrent deblocking threshold index; identifying a current minimumtransform block size corresponding to a current block boundary of thedecoded block in a current direction; and identifying a subset ofdeblocking thresholds from the set of deblocking thresholds based on thecurrent minimum transform block size as the current deblockingthreshold.
 7. The method of claim 6, wherein identifying the currentdeblocking threshold includes: in response to a determination that thecurrent minimum transform block size differs from a second minimumtransform block size for a second block boundary of the decoded blockopposite the current block boundary, identifying the current deblockingthreshold such that the current deblocking threshold differs from adeblocking threshold for the second block boundary; and in response to adetermination that the current minimum transform block size isequivalent to the second minimum transform block size, identifying thedeblocking threshold for the second block boundary as the currentdeblocking threshold.
 8. The method of claim 6, wherein deblockingincludes: in response to a current deblocking determination indicatingdeblocking for the current block boundary, deblocking the current blockboundary.
 9. The method of claim 8, wherein deblocking includesgenerating the current deblocking determination by: identifying acurrent flatness factor based on pixel values from the decoded blockalong the current direction; in response to a determination that thecurrent flatness factor exceeds a deblocking determination thresholdvalue from the current deblocking threshold, identifying the currentdeblocking determination as indicating the omission of deblocking;identifying an adjacent flatness factor based on pixel values from anadjacent decoded block along the current direction; in response to adetermination that the adjacent flatness factor exceeds the deblockingdetermination threshold value, identifying the current blockingdetermination as indicating the omission of deblocking; and in responseto a determination that the current flatness factor is within thedeblocking determination threshold value and the adjacent flatnessfactor is within the deblocking determination threshold value,identifying the current blocking determination as indicating deblocking.10. The method of claim 8, wherein deblocking the current block boundaryincludes: identifying a deblocking filter threshold from the subset ofdeblocking thresholds; identifying a deblocking filter parameter basedon the deblocking filter threshold; and deblocking the current blockboundary using the deblocking filter parameter.
 11. A method comprising:generating, by a processor executing instructions stored on anon-transitory computer-readable medium, an encoded frame by encoding aninput frame, wherein encoding includes: generating a decoded frame bydecoding the encoded frame; generating a reconstructed frame byreconstructing the decoded frame, wherein reconstructing the decodedframe includes: identifying a joint deblocking threshold index from aplurality of deblocking threshold indexes for deblocking the decodedframe; identifying a first deblocking threshold index from the pluralityof deblocking threshold indexes, wherein identifying the firstdeblocking threshold index includes using the joint deblocking thresholdindex as a second deblocking threshold index for deblocking the decodedframe; and identifying the second deblocking threshold index from theplurality of deblocking threshold indexes, wherein identifying thesecond deblocking threshold index includes using the first deblockingthreshold index for deblocking the decoded frame; and generating anoutput bitstream including the encoded frame, an indication of the firstdeblocking threshold index, and an indication of the second deblockingthreshold index; and outputting the output bitstream.
 12. The method ofclaim 11, wherein generating the output bitstream includes: includingthe indication of the first deblocking threshold index in a frame headercorresponding to the encoded frame.
 13. The method of claim 11, whereingenerating the output bitstream includes: identifying a differencebetween the first deblocking threshold index and the second deblockingthreshold index as a differential deblocking threshold index value; andincluding the differential deblocking threshold index value in theoutput bitstream.
 14. The method of claim 11, wherein generating thereconstructed frame includes: generating a decoded block by decoding anencoded block from the encoded frame; generating a reconstructed blockbased on the decoded block, wherein generating the reconstructed blockincludes deblocking based on the first deblocking threshold index andthe second deblocking threshold index; and including the reconstructedblock in the reconstructed frame.
 15. The method of claim 14, whereinencoding includes: on a condition that the first deblocking thresholdindex is a vertical deblocking threshold index, deblocking includesvertical deblocking based on the first deblocking threshold index andhorizontal deblocking based on the second deblocking threshold index;and on a condition that the first deblocking threshold index is ahorizontal deblocking threshold index, deblocking includes horizontaldeblocking based on the first deblocking threshold index and verticaldeblocking based on the second deblocking threshold index.
 16. Themethod of claim 14, wherein identifying the joint deblocking thresholdindex includes: determining joint error metrics, wherein each jointerror metric from the joint error metrics corresponds with deblockingthe decoded frame using a respective deblocking threshold index from theplurality of deblocking threshold indexes as the first deblockingthreshold index and the second deblocking threshold index; andidentifying the deblocking threshold index corresponding to a minimaljoint error metric from the joint error metrics as the joint deblockingthreshold index.
 17. The method of claim 16, wherein identifying thefirst deblocking threshold index includes: identifying first errormetrics, wherein each first error metric from the first error metricscorresponds with deblocking the decoded frame using the joint deblockingthreshold index as the second deblocking threshold index and using arespective deblocking threshold index from the plurality of deblockingthreshold indexes, other than the joint deblocking threshold index, asthe first deblocking threshold index; including the minimal joint errormetric in the first error metrics as a first error metric correspondingto the joint deblocking threshold index; and identifying the deblockingthreshold index corresponding to a minimal first error metric from thefirst error metrics as the first deblocking threshold index.
 18. Themethod of claim 17, wherein identifying the second deblocking thresholdindex includes: identifying second error metrics, wherein each seconderror metric from the second error metrics corresponds with deblockingthe decoded frame using the first deblocking threshold index and using arespective deblocking threshold index from the plurality of deblockingthreshold indexes, other than the first deblocking threshold index, asthe second deblocking threshold index; including the minimal first errormetric in the second error metrics as a second error metriccorresponding to the first deblocking threshold index; and identifyingthe deblocking threshold index corresponding to a minimal second errormetric from the second error metrics as the second deblocking thresholdindex.
 19. The method of claim 17, wherein deblocking includes:identifying a current deblocking threshold from a plurality ofdeblocking thresholds based on a current deblocking threshold index,wherein: on a condition that the current deblocking threshold index isthe first deblocking threshold index, the current deblocking thresholdis a first deblocking threshold; and on a condition that the currentdeblocking threshold index is the second deblocking threshold index, thecurrent deblocking threshold is a second deblocking threshold.
 20. Themethod of claim 19, wherein identifying the current deblocking thresholdincludes: identifying a set of deblocking thresholds from the pluralityof deblocking thresholds based on the current deblocking thresholdindex; identifying a current minimum transform block size correspondingto a current block boundary of the decoded block in a current direction;and identifying a subset of deblocking thresholds from the set ofdeblocking thresholds based on the current minimum transform block sizeas the current deblocking threshold.
 21. The method of claim 20, whereinidentifying the current deblocking threshold includes: in response to adetermination that the current minimum transform block size differs froma second minimum transform block size for a second block boundary of thedecoded block opposite the current block boundary, identifying thecurrent deblocking threshold such that the current deblocking thresholddiffers from a deblocking threshold for the second block boundary; andin response to a determination that the current minimum transform blocksize is equivalent to the second minimum transform block size,identifying the deblocking threshold for the second block boundary asthe current deblocking threshold.
 22. The method of claim 20, whereindeblocking includes: in response to a current deblocking determinationindicating deblocking for the current block boundary, deblocking thecurrent block boundary.
 23. The method of claim 22, wherein deblockingincludes generating the current deblocking determination by: identifyinga current flatness factor based on pixel values from the decoded blockalong the current direction; in response to a determination that thecurrent flatness factor exceeds a deblocking determination thresholdvalue from the current deblocking threshold, identifying the currentdeblocking determination as indicating the omission of deblocking;identifying an adjacent flatness factor based on pixel values from anadjacent decoded block along the current direction; in response to adetermination that the adjacent flatness factor exceeds the deblockingdetermination threshold value, identifying the current blockingdetermination as indicating the omission of deblocking; and in responseto a determination that the current flatness factor is within thedeblocking determination threshold value and the adjacent flatnessfactor is within the deblocking determination threshold value,identifying the current blocking determination as indicating deblocking.24. The method of claim 22, wherein deblocking the current blockboundary includes: identifying a deblocking filter threshold from thesubset of deblocking thresholds; identifying a deblocking filterparameter based on the deblocking filter threshold; and deblocking thecurrent block boundary using the deblocking filter parameter.
 25. Amethod comprising: generating, by a processor in response toinstructions stored on a non-transitory computer-readable medium, areconstructed frame by: generating a decoded frame including decodedblocks by decoding a portion of an encoded bitstream; identifying afirst deblocking threshold index from the encoded bitstream; identifyinga second deblocking threshold index from the encoded bitstream, thesecond deblocking threshold index differing from the first deblockingthreshold index; generating a partially deblocked frame by deblockingthe decoded frame in a first direction based on the first deblockingthreshold index; and generating the reconstructed frame by deblockingthe partially deblocked frame in a second direction based on the seconddeblocking threshold index; and outputting the reconstructed frame. 26.The method of claim 25, wherein: identifying the first deblockingthreshold index includes extracting the first deblocking threshold indexfrom a frame header corresponding to the reconstructed frame;identifying the second deblocking threshold index includes: extractinginformation indicating the second deblocking threshold index from theframe header corresponding to the reconstructed frame; in response to adetermination that the information indicating the second deblockingthreshold index includes a differential deblocking threshold indexvalue, identifying a sum of the differential deblocking threshold indexvalue and the first deblocking threshold index as the second deblockingthreshold index; and in response to a determination that the informationindicating the second deblocking threshold index includes a deblockingthreshold index, identifying the deblocking threshold index as thesecond deblocking threshold index.